The present invention relates to multi-layer composites of two or more polymeric layers, at least one of which is formed from a thermosetting composition, the composite comprising at least a first polymeric layer formed on a substrate and a second polymeric formed over at least a portion of the first polymeric layer, wherein in the absence of an adhesion promoter composition, the first polymeric layer and the second polymeric layer have poor interlayer adhesion. The present invention also relates to curable coating compositions used to form multi-layer composites, to methods for improving the interlayer adhesion of such multi-layer composites and to coated substrates.
Color-plus-clear coating systems involving the application of a colored or pigmented basecoat to a substrate followed by application of a transparent or clearcoat over the basecoat have become increasingly popular as original finishes for a number of consumer products including, for example, automotive vehicles. The color-plus-clearcoating systems have outstanding appearance properties such as gloss and distinctness of image, due in large part to the clearcoat. Such color-plus-clearcoating systems have become popular for use with automotive vehicles, aerospace applications, floor coverings such as ceramic tiles and wood flooring, packaging coatings and the like.
Topcoat coating compositions, particularly those used to form the transparent clearcoat in color-plus-clearcoating systems for automotive applications, are subject to defects that can occur during the assembly process, as well as damage from numerous environmental elements. Such defects which can occur during the assembly process include paint defects which can occur during the application or curing of the basecoat and/or the clearcoat. Damaging environmental elements include acidic precipitation, exposure to ultraviolet radiation from sunlight, high relative humidity and high temperatures, defects due to contact with objects causing scratching of the coated surface, and defects due to impact with small, hard objects resulting in chipping of the coating surface.
Further, elastomeric automotive parts and accessories, for example, elastomeric bumpers and body side moldings, are typically coated xe2x80x9coff sitexe2x80x9d and shipped to automobile assembly plants. The coating compositions applied to such elastomeric substrates are typically formulated to be very flexible so the coating can bend or flex with the substrate without cracking. To achieve the requisite flexibility, coating compositions for use on elastomeric substrates often are formulated to produce coatings with lower crosslink densities or to include flexibilizers which act to lower the overall film glass transition temperature (Tg). While acceptable flexibility properties can be achieved with these formulating techniques, they also can result in softer films that are susceptible to scratching. Consequently, great expense and care must be taken to package the coated parts to prevent scratching of the coated surfaces during shipping to automobile assembly plants.
U.S. Pat. No. 6,235,858 B1 discloses carbamate and/or urea functional polymers for use in coating compositions, especially clear coating compositions for color-plus-clear coating systems. Such polymers provide coatings with good resistance to damage caused by acidic precipitation.
U.S. Pat. No. 5,853,809 discloses clearcoats in color-plus-clear systems which have improved scratch resistance due to the inclusion in the coating composition of inorganic particles such as colloidal silicas which have been surface modified with a reactive coupling agent via covalent bonding.
A number of patents disclose the use of a surface active material, for example, a polysiloxane, in coating compositions to improve mar resistance of the cured coatings. U.S. Pat. Nos. 5,939,491 and 6,225,434B1 disclose coating compositions comprising organic polysiloxanes having reactive functional groups. These polysiloxanes provide coatings with improved mar and scratch resistance.
A number of patents disclose the use of boric acid in polymeric compositions. For example, U.S. Pat. Nos. 5,951,747 and 6,059,867 discloses the use of boric acid and borates in conjunction with a succinate in non-chromate, corrosion-inhibiting coating compositions for improved adhesion to metallic surfaces. Such compositions further include inhibitors such as phosphates, phosphosilicates, silicates, titanates, and zinc salts. U.S. Pat. No. 4,832,990 discloses a process for improving adhesion of polyolefins to metal substrates comprising mechanical cleaning of the metal surface, treating the metal surface with a water-alcohol solution containing an alkoxysilane and boric acid, thermally treating the acid treated substrate, and subsequently treating the substrate with a polyolefin-based composition comprising zeolites and carbon black pigment. U.S. Pat. No. 5,073,455 discloses a thermoplastic laminated film which has improved adhesion to hydrophilic polymers, hydrophobic polymers and inorganic substances. The film comprise a base film of thermoplastic resin and a layer formed on the base film comprising a composition of one or more of water-soluble resins, water emulsified resins and water-dispersible resins, and an organic boron polymer or a mixture composed of an organic boron polymer and vinyl alcohol.
Other multi-layer composite coatings are commonplace in modern coating lines. For example, a typical automotive coating system can include the sequential application of an electrodeposition primer, a primer-surfacer, a color enhancing base coat, and a transparent top coat. In some instances, the electrodeposition primer is applied over a mill-applied weldable, thermosetting coating which has been applied to the coiled steel metal substrate from which the automobile body (or body parts, such as fenders, doors and hoods) has been formed. Also, adhesive coatings, for example, windshield adhesives, trim and molding adhesives and structural adhesives are sometimes applied to the cured top coats where necessary. Due to these multi-layer composite coating processes, it is necessary that the previously applied coating layer have excellent intercoat or interlayer adhesion to the subsequently applied coating layer(s).
Although the aforementioned coating compositions exhibit improvements for acid etch resistance and mar and scratch resistance, such compositions may not be readily recoatable. That is, when a subsequent coating is applied to the cured mar and scratch resistant coating composition, the intercoat adhesion between the cured coating and the subsequently applied coating can be quite poor.
For example, as mentioned above, on most vehicle coating lines the vehicle body is first given a corrosion inhibitive electrodepositable primer coating commonly formed from a cationic electrodepositable coating composition. This electrodeposition primer is fully cured and, a primer-surfacer is typically applied to the cured electrodeposition primer. The primer-surfacer serves to enhance chip resistance of subsequently applied top coatings as well as to ensure good appearance of the top coatings. The electrodepositable primer must have excellent interlayer, i.e., intercoat, adhesion to the subsequently applied primer-surfacer coating. The top coats, which can include a monocoats as well as a color-plus-clear coating system, are then applied to the cured primer-surfacer coating. While most top coats have excellent intercoat adhesion to the primer-surfacer coating, some top coating compositions inherently may exhibit intercoat adhesion problems with some primer-surfacer coatings.
Also, due to the resultant cost-savings, there is recent interest in the automotive coatings market in eliminating the primer-surfacer step altogether. That is, the top coats can be directly applied to the cured electrodeposition primer. In such modified coating processes, the electrodeposition primer is required to meet stringent durability and appearance specifications. Moreover, the cured electrodepositable primer must have excellent intercoat adhesion to the subsequently applied top coats (either monocoats or color coats of a color-plus-clear system).
On commercial automobile coating lines, during application of the coating system, certain portions of the line can experience process problems. For example, the clearcoat applicator might malfunction, or curing ovens can widely vary in temperature from the specification temperature. While the color coat typically is xe2x80x9cflash curedxe2x80x9d to drive off solvent, but not fully cure the coating, once the clear coating has been applied, the color-plus-clear coating system typically is given a full cure (e.g., 250xc2x0 F. (121xc2x0 C.) for 20 minutes) to simultaneously cure both the base coat and the top coat. In instances where the clear coat application system is malfunctioning, the auto body with the applied color coat will continue through the clear coat applicator station and into the clear coat curing oven, thereby fully curing the color coat. If this occurs, some automobile manufacturers elect to reapply the color coat over the fully cured color coat prior to application of the clearcoat. In such situations, the fully cured color coat can have poor intercoat adhesion with the subsequently applied color coat, even though the compositions may be the same.
Also, windshields and other items such as trim moldings typically are affixed to the body of a vehicle with an adhesive material, typically a moisture-cured material containing isocyanate group-containing polymers. Motor Vehicle Safety Standards (MVSS) require that these adhesives have complete adhesion to both the windshield and the coated substrate to which they are applied. Similar adhesive compositions can be used as structural adhesives as well. Such adhesives, for example, are commercially available from Essex Specialty Products, Inc. of Auburn Hills, Mich. These adhesive products adhere well to many cured top coating compositions used to coat vehicles such as automobiles. It is known, however, that these adhesive materials often do not completely adhere to some top coats, for example, those formed from coating compositions based on carbamate and/or urea containing polymers. This necessitates the application of a primer coating to the cured carbamate and/or urea-based top coatings prior to application of the windshield adhesive to ensure compliance with the aforementioned Motor Vehicle Safety Standards. Such primer coatings are typically based on moisture-curable polymers similar to those comprising the adhesive. Use of such primer coatings has proven to be effective, but primer coating application adds an additional and expensive step to the windshield and/or trim installation processes.
Moreover, as discussed previously, during the assembly process, the applied color-plus-clear coating can include surface defects in the clear coat surface which requires repair. Some automobile manufacturers elect to remove the defect and recoat the repair area with the same clear coat composition. In this instance, the cured clear coat must have excellent intercoat adhesion to the subsequently applied clear coat. It is known, however, that some clear coats when cured have poor intercoat adhesion with the subsequently applied repair clear coat.
In view of the foregoing, there remains a need in the coating industry for coating compositions which have improved properties such as acid etch resistance and mar and scratch resistance while maintaining excellent intercoat or interlayer adhesion to subsequently applied coatings and/or adhesives.
Also, many adhesion promoters are known in the art. Such adhesion promoters include, for example, phosphatized epoxy compounds, for example, the reaction product formed from phosphoric acid and a bisphenol A or hydrogenated bisphenol A diglycidyl ether. Typically, such adhesion promoters are useful for promoting adhesion of coating layers which contain them to a substrate, for example, a metallic substrate or an elastomeric substrate or to a previously applied coating layer. Also, such adhesion promoters can be used advantageously to promote cohesive integrity within a coating layer, for example, the cohesive integrity of a metal flake-containing basecoat. Further, it is known that adhesion promoter compositions, such as a phosphate wipe or an adhesion-promoting primer, can be topically applied to a cured coating to provide an adhesion promoting layer thereover, thereby improving adhesion of a subsequently applied coating. This, however, necessitates an additional and costly coating step in the coating application process. It is not known, however, to include an adhesion promoter as a component in a coating composition which will migrate during a curing reaction through the surrounding polymeric matrix to the surface of the resultant coating thereby promoting the interlayer or intercoat adhesion between the resultant coating and a subsequently applied coating.
As mentioned above, the surface of a coating can be modified by the inclusion of one or more surface active agents, for example, silicone oils, siloxanes, and fluorosurfactants, in the coating compositions to improve such properties as slip and mar resistance of such coatings. Typical surface active agents have solubility parameters or surface energies which are sufficiently different from the coating compositions (i.e., the composition without the surface active agent) such that, when included in the composition, the surface active agent can migrate or partition to the surface region of the cured coating as the composition cures. That is, the surface active agent is present at the surface region of the resultant coating layer. While such surface-modified coatings can exhibit improved slip and mar resistance, they often are difficult to recoat. Hence, the interlayer or intercoat adhesion with a subsequently applied coating is poor, sometimes resulting in delamination.
It has now been found that by selecting adhesion promoting components and surface active agents such that the solubility parameter of the coating composition containing both the adhesion promoting component and the surface active agent is sufficiently different from that of an analogous coating composition which does not contain the adhesion promoting component and the surface active agent, that the adhesion promoting component partitions to the surface region of the resultant coating. This can result in a concentration of the adhesion promoting component at the surface region which is greater than the concentration in the interior or bulk region of the coating layer. This partitioning effect of the adhesion promoting component can significantly increase its effect in promoting the adhesion of the coating layer which contains the adhesion promoter to a subsequently applied coating layer, as well as to the substrate to which it is applied.
In one embodiment, the present invention provides an improved multi-layer composite comprising at least a first polymeric layer and a second polymeric layer formed over the first polymeric layer thereby forming an interface region there between. At least one of the polymeric layers is formed from a thermosetting composition comprising an adhesion promoter composition. The adhesion promoter composition comprises (1) at least one adhesion promoting component, and (2) at least one surface active component. The improvement comprises the presence of the adhesion promoting component (1) at the interface region.
In a further embodiment, the present invention is directed to an improved multi-layer composite comprising at least a first polymeric layer and a second polymeric layer formed over the first polymeric layer thereby forming an interface region there between. The first polymeric layer has a surface region and a bulk region and is formed from a thermosetting composition. The thermosetting composition is formed from the following components: (A) at least one polymer comprising one or more reactive functional groups selected from at least one of a hydroxyl group and a carbamate group; (B) at least one curing agent selected from at least one of an aminoplast resin, a polyisocyanate and a blocked isocyanate; and (C) at least one adhesion promoter composition comprising (1) at least one adhesion promoting component selected from at least one of boric acid, boric acid equivalents, and mixtures thereof, and (2) at least one surface active component comprising a least one polysiloxane comprising at least one of the following structural units (I):
R1nR2mSiO(4xe2x88x92nxe2x88x92m)/2xe2x80x83xe2x80x83(I)
wherein each R1, which may be identical or different, represents H, OH, a monovalent hydrocarbon group or a monovalent siloxane group; each R2, which may be identical or different, represents a group comprising one or more active hydrogens; and m and n each represent a positive number fulfilling the requirements of 0 less than m less than 4; 0 less than n less than 4; and 2xe2x89xa6(m+n) less than 4. The improvement comprises the presence of the adhesion promoting component (1) at the interface region.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term xe2x80x9cabout.xe2x80x9d Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of xe2x80x9c1 to 10xe2x80x9d is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.
As previously mentioned, In one embodiment, the present invention provides an improved multi-layer composite comprising at least a first polymeric layer and a second polymeric layer formed over the first polymeric layer thereby forming an interface region there between. At least one of the polymeric layers is formed from a thermosetting composition comprising an adhesion promoter composition. The adhesion promoter composition comprises (1) at least one adhesion promoting component, and (2) at least one surface active component. The improvement comprises the presence of the adhesion promoting component (1) at the interface region. The adhesion promoting component (1) typically is present in the interface region in an amount sufficient to improve the interlayer (or intercoat) adhesion between the first and second polymeric layers.
The adhesion promoter composition comprises at least one adhesion promoting component (1) and at least one surface active component (2). It should be understood that the adhesion promoter composition can comprise the adhesion promoting component (1) and the surface active component as separate components in an admixture; or the adhesion promoter composition can comprise a reaction product formed from the adhesion promoting component (1) and the surface active component (2). Obviously, the adhesion promoter composition can comprise the above described reaction product formed from components (1) and (2), as well as the component (1) and the component (2), all present as three separate ingredients.
In one particular embodiment, the thermosetting composition used to form one or more of the polymeric layers is such that the free energy of mixing value for an admixture of the adhesion promoter composition and the analogous thermosetting composition without the adhesion promoter composition is a positive value. In another embodiment of the present invention, the solubility parameter of the adhesion promoter composition is sufficiently different from the solubility parameter of the analogous thermosetting composition without the adhesion promoter composition, such that the resulting thermodynamic interaction parameter value ("khgr") for the admixture of the adhesion promoter composition and the thermosetting composition which does not include the adhesion promoter composition is 0.5 or greater.
The xe2x80x9cfree energy of mixingxe2x80x9d is defined as xcex94G=xcex94Hxe2x88x92Txcex94S, where G is the Gibb""s free energy, H is enthalpy, S is entropy and T is temperature. Simply put, when the free energy of mixing (xcex94G) of two components is a positive value, the two components are immiscible and will phase separate, For example, in the instance where a coating composition contains these two substantially immiscible components, when applied as a coating layer one component will tend to migrate or partition to the surface region of the coating layer while the other will remain in the bulk. region. Also, xcex94G for a binary mixture containing a component 1 and a component 2 may be defined by the following equation:
xcex94G=RT[(n1lnX1+n2lnX2)+"khgr"n1X2]
where R is the gas constant, T is temperature, X is the volume fraction of component 1 or 2, n is the number of particles, and "khgr" (xe2x80x9cchixe2x80x9d) represents the thermodynamic interaction parameter. The thermodynamic interaction parameter ("khgr" or xe2x80x9cchixe2x80x9d) is defined as the difference in the energy of mixing of components 1 and 2. This can be represented by the following equation:
"khgr"=(xcex94Emix/RT)Vm
where Vm is the average molar volume (xe2x80x9creference segment volumexe2x80x9d) and R and T are defined above. xe2x80x9cChixe2x80x9d may also be defined as the difference in solubility parameter (SP) of two materials as follows:
"khgr"=Vm(xcex41xe2x88x92xcex42)2/RT
where xcex4 is the Hildebrand solubility parameter. The solubility parameter may be computed from a value known as the cohesive energy density (xe2x80x9ccedxe2x80x9d) of a material. The xe2x80x9ccedxe2x80x9d is related to the heat of vaporization of a material, that is, how much energy is required to remove a single molecule from the bulk. For polymeric systems, such as a coating composition, where the assumption that the entropy of mixing is exceedingly small, the free energy expressions reduce to the energy of mixing itself, that is xcex94G=xcex94H, and a theoretical critical point exists where two materials become immiscible (phase separate) when xe2x80x9cchixe2x80x9d is greater than 0.5. For regular solutions, (i.e., of low molecular weight species) this critical point has a value of 2.0.
To summarize, from first principles, the xe2x80x9ccedxe2x80x9d for a bulk material can be computed. The xe2x80x9ccedxe2x80x9d is directly related to the solubility parameter (xcex4) as indicated above. The thermodynamic interaction parameter xe2x80x9cchixe2x80x9d ("khgr") can be computed from the differences in the solubility parameter (xcex4) for each of the two materials. xe2x80x9cChixe2x80x9d along with relative fractions of materials in a mixture may be used to compute the free energy of mixing (xcex94G). If xcex94G is a positive value, the mixture is thermodynamically unstable and phase separation will occur. Critical points for this condition are values of xe2x80x9cchixe2x80x9d is equal to 0.5 and greater for higher molecular weight materials such as the polymeric components of a resinous binder system, and 2.0 for smaller molecules. Flory, Paul J., Principles of Polymer Chemistry, Cornell University Press (1953), Chapters XII and XIII; Polymer User Guide, September 1996, Molecular Simulations, Inc., San Diego, Calif.; Nicolaides, D., Parameterisation for Mesoscale Modeling, Molecular Simulations, Inc.
Without intending to be bound by any theory, it is believed that by such phase separation discussed above, the adhesion promoting component (1) a can be present in the interface region between the first polymer layer and the second polymer layer, thereby providing improved interlayer adhesion between the two.
In one embodiment of the present invention, the first polymeric layer is formed from the thermosetting composition, typically over a substrate, and comprises a surface region and a bulk region. As used herein xe2x80x9csurface regionxe2x80x9d of the cured thermosetting composition (or of the resultant polymeric layer) means the region which is generally parallel to the exposed air-surface interface of the cured composition (typically formed on a substrate) and which has thickness generally extending perpendicularly from the surface of the cured polymeric layer to a depth ranging from at least 20 nanometers to 200 nanometers beneath the exposed surface. In certain embodiments, this thickness of the surface region ranges from at least 20 nanometers to 100 nanometers, and can range from at least 20 nanometers to 50 nanometers. As used herein, xe2x80x9cbulk regionxe2x80x9d of the cured thermosetting composition (or the resultant polymeric layer) means the region which extends beneath the surface region and which is generally parallel to the surface of the substrate to which the composition has been applied. The bulk region has a thickness extending from its interface with the surface region through the cured composition to the substrate or polymeric layer beneath the cured composition.
In another embodiment of the present invention, a free energy of mixing value of an admixture of the adhesion promoter composition and the thermosetting composition without the adhesion promoter composition is a positive value such that the adhesion promoting component (1) is partitioned within the first polymeric layer to provide a concentration of the adhesion promoting component (1) at the surface region which is greater than the concentration of the adhesion promoting component (1) within the bulk region of the polymeric layer.
In yet another embodiment of the present invention, the solubility parameter of the adhesion promoter composition is sufficiently different from the solubility parameter of the thermosetting composition without the adhesion promoter composition, such that the thermodynamic interaction parameter value for the admixture of the adhesion promoter composition and the thermosetting composition without the adhesion promoter composition is greater than 0.5, thereby causing the adhesion promoting component (1) to partition within the first polymeric layer to provide a concentration of the adhesion promoting component (1) at the surface region which is greater than the concentration of the adhesion promoting component (1) in the bulk region of the first polymeric layer.
In one embodiment of the present invention, the thermosetting composition, for example, a curable coating composition, comprises (A) at least one polymer comprising at least one reactive functional group, such as those described in detail below, (B) at least one curing agent having at least one functional group reactive with the functional groups of (A), and (C) at least one adhesion promoter composition, wherein the adhesion promoting component (1) is selected from at least one of boron, aluminum, titanium, zirconium, phosphorous, and silicon. Typically, the adhesion promoting component (1) comprises a compound selected from at least one of a borate, an aluminate, a titanate, a zirconate, an inorganic acid or ester of phosphorous, a silicate, a siloxane, a silane and mixtures thereof. Typically, the at least one adhesion promoting component (1) is selected from at least one of a borate and an aluminate.
Examples of suitable borates are those discussed below in detail. Examples of titanates suitable for use in the compositions of the present invention include titanium isopropoxide, isopropyl triostearoyl titanate, dicyclo(dioct)pyrophosphato titanate, tetraisopropyl di(dioctyl)phosphito titanate. Suitable aluminates include aluminum alkoxides such as aluminum isopropoxide, which is typically employed, and aluminum acetylacetonate, Suitable examples of inorganic acids or esters of phosphorous include, for example, phosphoric acid esters, phosphinic acids, phosphorous acid esters, and phosphonic acids. Exemplary of a suitable silicate is tetraethyl orthosilicate. Suitable siloxanes include tetraisopropyidisiloxanes and tetramethylsiloxane. Suitable silanes include tetramethyl silyl ethers.
In one embodiment of the present invention, a polysiloxane (2) comprising one or more hydroxyl functional groups is employed as the surface active component, In one particular embodiment of the invention, the adhesion promoting component (1) comprises an aluminum alkoxide, such as aluminum triisopropoxide, and the surface active component (2) comprises a polysiloxane comprising one or more groups comprising active hydrogens.
Other materials suitable for use as the surface active component (2) are any of the surface active agents well known in the art. As used herein, by xe2x80x9csurface active agentxe2x80x9d is meant any material which tends to lower the solid surface tension or surface energy of the xe2x80x9ccuredxe2x80x9d composition or coating. That is, the cured composition or coating formed from a composition comprising a surface active agent has a lower solid surface tension or surface energy than a cured coating formed from the analogous composition which does not contain the surface active agent.
For purposes of the present invention, solid surface tension can be measured according to the Owens-Wendt method using a Rame""-Hart Contact Angle Goniometer with distilled water and methylene iodide as reagents. Generally, a 0.02 cc drop of one reagent is placed upon the cured coating surface and the contact angle and its complement are measured using a standard microscope equipped with the goniometer. The contact angle and its complement are measured for each of three drops. The process is then repeated using the other reagent. An average value is calculated for the six measurements for each of the reagents. The solid surface tension is then calculated using the Owens-Wendt equation:
{xcex3|(1+cos "PHgr")}/2=(xcex3|dxcex3sd)1/2+(xcex3|pxcex3sp)1/2
where xcex3l is the surface tension of the liquid (methylene iodide=50.8, distilled water=72.8) and xcex3d and xcex3p are the dispersion and polar components (methylene iodide xcex3d=49.5, xcex3p=1.3; distilled watery xcex3d=21.8, xcex3p=51.0); the values for "PHgr" measured and the cos "PHgr" determined. Two equations are then setup, one for methylene iodide and one for water. The only unknowns are xcex3sd and xcex3sp. The two equations are then solved for the two unknowns. The two components combined represent the total solid surface tension.
The surface active component (2) can be selected from amphiphilic, reactive functional group-containing polysiloxanes such as are described below, amphiphilic fluoropolymers, and mixtures of any of the foregoing. With reference to water-soluble or water-dispersible amphiphilic materials, the term xe2x80x9camphiphilicxe2x80x9d means a polymer having a generally hydrophilic polar end and a water-insoluble generally hydrophobic end. Nonlimiting examples of suitable functional group-containing polysiloxanes for use as surface active agents include those polysiloxanes described above. Nonlimiting examples of suitable amphiphilic fluoropolymers include fluoroethylene-alkyl vinyl ether alternating copolymers (such as those described in U.S. Pat. No. 4,345,057) available from Asahi Glass Company under the tradename LUMIFLON; fluorosurfactants, such as the fluoroaliphatic polymeric esters commercially available from 3M of St. Paul, Minn. under the tradename FLUORAD; functionalized perfluorinated materials, such as 1H,1H-perfluoro-nonanol commercially available from FluoroChem USA; and perfluorinated (meth)acrylate resins. Nonlimiting examples of other adjuvant surface active agents suitable for use in the composition or coating of the present invention can include anionic, nonionic and cationic surface active agents.
Nonlimiting examples of suitable anionic surface active agents include sulfates or sulfonates. Specific nonlimiting examples include higher alkyl mononuclear aromatic sulfonates such as the higher alkyl benzene sulfonates containing from 10 to 16 carbon atoms in the alkyl group and a straight- or branched-chain, e.g., the sodium salts of decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl or hexadecyl benzene sulfonate and the higher alkyl toluene, xylene and phenol sulfonates; alkyl naphthalene sulfonate, and sodium dinonyl naphthalene sulfonate. Other nonlimiting examples of suitable anionic surface active agents include olefin sulfonates, including long chain alkenylene sulfonates, long chain hydroxyalkane sulfonates, and mixtures of any of the foregoing. Nonlimiting examples of other sulfate or sulfonate detergents are paraffin sulfonates such as the reaction products of alpha olefins and bisulfites (e.g., sodium bisulfite). Also comprised are sulfates of higher alcohols, such as sodium lauryl sulfate, sodium tallow alcohol sulfate, or sulfates of mono-or di-glycerides of fatty acids (e.g., stearic monoglyceride monosulfate), alkyl poly(ethoxy)ether sulfates including, but not limited to, the sulfates of the condensation products of ethylene oxide and lauryl alcohol (usually having 1-5 ethenoxy groups per molecule); lauryl or other higher alkyl glyceryl ether sulfonates; aromatic poly(ethenoxy)ether sulfates including, but not limited to, the sulfates of the condensation products of ethylene oxide and nonyl phenol (usually having 1-20 oxyethylene groups per molecule). Further nonlimiting examples include salts of sulfated aliphatic alcohol, alkyl ether sulfate or alkyl aryl ethoxy sulfate available from Rhone-Poulenc under the general tradename ABEX. Phosphate mono-or di-ester type anionic surface active agents also can be used. These anionic surface active agents are well known in the art and are commercially available under the general trade designation GAFAC from GAF Corporation and under the general trade designation TRITON from Rohm and Haas Company.
Nonlimiting examples of nonionic surface active agents suitable for use in the cured composition or coating of the present invention include those containing ether linkages and which are represented by the following general formula: RO(R""O)nH; wherein the substituent group R represents a hydrocarbon group containing 6 to 60 carbon atoms, the substituent group Rxe2x80x2 represents an alkylene group containing 2 or 3 carbon atoms, and mixtures of any of the foregoing, and n is an integer ranging from 2 to 100. Such nonionic surface active agents can be prepared by treating fatty alcohols or alkyl-substituted phenols with an excess of ethylene or propylene oxide. The alkyl carbon chain may contain from 14 to 40 carbon atoms and may be derived from a long chain fatty alcohol such as oleyl alcohol or stearyl alcohol. Nonionic polyoxyethylene surface active agents of the type represented by the formula above are commercially available under the general trade designation SURFYNOL(copyright) from Air Products Chemicals, Inc.; PLURONIC(copyright) or TETRONIC(copyright) from BASF Corporation; TERGITOL(copyright) from Union Carbide; and SURFONIC(copyright) from Huntsman Corporation. Other nonlimiting examples of suitable nonionic surface active agents include block copolymers of ethylene oxide and propylene oxide based on a glycol such as ethylene glycol or propylene glycol including, but not limited to, those available from BASF Corporation under the general trade designation PLURONIC(copyright).
As indicated above, cationic surface active agents also can be used. Nonlimiting examples of cationic surface active agents suitable for use in the compositions of the present invention include acid salts of alkyl amines such as ARMAC(copyright) HT, an acetic acid salt of n-alkyl amine available from Akzo Nobel Chemicals; imidazoline derivatives such as CALGENE(copyright) C-100 available from Calgene Chemicals Inc.; ethoxylated amines or amides such as DETHOX(copyright) Amine C-5, a cocoamine ethoxylate available from Deforest Enterprises; ethoxylated fatty amines such as ETHOX(copyright) TAM available from Ethox Chemicals, Inc.; and glyceryl esters such as LEXEMUL(copyright) AR, a glyceryl stearate/stearaidoethyl diethylamine available from Inolex Chemical Co.
Other examples of suitable surface active agents can include polyacrylates. Nonlimiting examples of suitable polyacrylates include homopolymers and copolymers of acrylate monomers, for example polybutylacrylate and copolymers derived from acrylate monomers (such as ethyl (meth)acrylate, 2-ethylhexylacrylate, butyl (meth)acrylate and isobutyl acrylate), and hydroxy ethyl(meth)acrylate and (meth)acrylic acid monomers. In one embodiment, the polyacrylate can have amino and hydroxy functionality. Suitable amino and hydroxyl functional acrylates are disclosed in Example 26 below and in U.S. Pat. No. 6,013,733, which is incorporated herein by reference. Another example of a useful amino and hydroxyl functional copolymer is a copolymer of hydroxy ethyl acrylate, 2-ethylhexylacrylate, isobutyl acrylate and dimethylamino ethylmethacrylate. In another embodiment, the polyacrylate can have acid functionality, which can be provided, for example, by including acid functional monomers such as (meth)acrylic acid in the components used to prepare the polyacrylate. In another embodiment, the polyacrylate can have acid functionality and hydroxyl functionality, which can be provided, for example, by including acid functional monomers such as (meth)acrylic acid and hydroxyl functional monomers such as hydroxy ethyl (meth)acrylate in the components used to prepare the polyacrylate.
In the multi-layer composite of the present invention, the compound (C), which typically comprises a compound selected from at least one of an aluminum alkoxide or a boron-containing compound such as those described in detail above is present in one or both of the first and second polymeric layers in an amount sufficient to improve the interlayer adhesion between the first and the second polymeric layers. That is, when the compound (C) is present in one or both of the polymeric layers, the delamination or adhesion loss, as determined in accordance with ASTM-3359-97, method B, of the second polymeric layer from the first polymer layer can be increased by one or more numerical units of the rating scale specified in the aforementioned method.
In a further embodiment, the present invention is directed to an improved multi-layer composite comprising at least a first polymeric layer and a second polymeric layer formed over the first polymeric layer thereby forming an interface region there between. The first polymeric layer has a surface region and a bulk region and is formed from a thermosetting composition. The thermosetting composition is formed from the following components: (A) at least one polymer comprising one or more reactive functional groups selected from at least one of a hydroxyl group and a carbamate group; (B) at least one curing agent selected from at least one of an aminoplast resin, a polyisocyanate and a blocked isocyanate; and (C) at least one adhesion promoter composition comprising (1) at least one adhesion promoting component selected from at least one of boric acid, boric acid equivalents, and mixtures thereof, and (2) at least one surface active component comprising a least one polysiloxane comprising at least one of the following structural units (I):
R1nR2mSiO(4xe2x88x92nxe2x88x92m)/2xe2x80x83xe2x80x83(I)
wherein each R1, which may be identical or different represents H, OH, a monovalent hydrocarbon group or a monovalent siloxane group; each R2, which may be identical or different, represents a group comprising one or more active hydrogens; and m and n each represent a positive number fulfilling the requirements of 0 less than m less than 4; 0 less than n less than 4; and 2xe2x89xa6(m+n) less than 4. The improvement comprises the presence of the adhesion promoting component (A) at the interface region. In one embodiment of the present invention, R2 represents ORxe2x80x2, where Rxe2x80x2 represents H or an alkyl group having 1 to 20 carbon atoms.
As used herein, by xe2x80x9cinterface regionxe2x80x9d in meant the area where a major surface of the first polymeric layer contacts an opposing major surface of the second polymeric layer. Of course, where one or both of the polymeric layers is formed from a thermosetting composition, this xe2x80x9cinterface regionxe2x80x9d can include an xe2x80x9cinterphase regionxe2x80x9d which is formed by the intermingling or slight solubilization of the composition used to form the first polymeric layer with the composition used to form the second polymeric layer. The interface region can comprise an area extending up to 200 nanometers into the bulk region from a major surface of the first polymeric layer and up to 200 nanometers into the bulk region from the major surface of the second polymeric layer, where the major surfaces of the first and second polymeric layers are in contact with one another.
In one embodiment, the present invention provides an improved multi-layer composite of two or more polymeric layers at least one of which is formed from a thermosetting composition. The composite comprises at least a first polymeric layer formed on a substrate and a second polymeric layer over at least a portion of said first polymeric layer, wherein in the absence of an adhesion promoter composition, typically a boron-containing compound, the first polymeric layer and the second polymeric layer have poor interlayer adhesion. The improvement comprises the inclusion of at least one adhesion promoter composition comprising a boron-containing compound selected from boric acid, boric acid equivalents, and mixtures thereof in one or both of the first and second polymeric layers in an amount sufficient to improve the interlayer adhesion of the first and second polymeric layers.
It should be understood that the composite of the present invention can comprise only two polymeric layers, wherein the first polymeric layer is formed on at least a portion of a substrate and the second polymeric layer is formed over at least a portion of the first polymeric layer. Alternatively, the composite of the present invention can comprise the first polymeric layer over at least a portion of a substrate, and the second polymeric layer formed over at least a portion of the first polymeric layer, where there are one or more subsequent polymeric layers formed over at least a portion of the second polymeric layer.
For example, the first polymeric layer can comprise a primer-surfacer coating and the second polymeric layer can comprise a color-enhancing base coating to which has been subsequently applied a transparent top coat. Also, the first polymeric layer can comprise an electrodepositable primer coating and the second polymeric layer can comprise a primer-surfacer coating to which has been subsequently applied an appearance enhancing monocoat or a color-plus-clear coating system. Additionally, the first polymeric layer can comprise a transparent clear coat (as the clear coat in a color-plus-clear coating system) and the second polymeric layer can comprise a repair clear coat.
Also, it should be understood that as used herein, a polymeric layer or composition formed xe2x80x9coverxe2x80x9d at least a portion of a xe2x80x9csubstratexe2x80x9d refers to a polymeric layer or composition formed directly on at least a portion of the substrate surface, as well as a polymeric layer or composition formed over any coating or adhesion promoter material which was previously applied to at least a portion of the substrate.
That is, the xe2x80x9csubstratexe2x80x9d upon which the first polymeric layer has been formed can comprise a metallic or elastomeric substrate to which one or more coating layers have been previously applied. For example, the xe2x80x9csubstratexe2x80x9d can comprise a metallic substrate and a weldable primer coating over at least a portion of the substrate surface, and the first polymeric layer can comprise an electrodepositable primer coating. Likewise, the xe2x80x9csubstratexe2x80x9d can comprise a metallic substrate having an electrodepositable primer formed over at least a portion thereof, and a primer-surfacer coating over at least a portion of the electrodepositable primer. The first polymeric layer can comprise, for example, a pigmented base coat over at least a portion of this multi-layer xe2x80x9csubstratexe2x80x9d, and the second polymeric layer can comprise a pigment-free top coat formed over at least a portion of the pigmented base coat.
At least one of the first and second polymeric layers is formed from a thermosetting composition. In the multi-layer composite of the present invention, the first polymeric only can comprise a thermosetting composition, the second layer only can comprise a thermosetting composition, or, alternatively both the first and second polymeric layers can comprise a thermosetting composition. In the latter instance, the thermosetting composition from which the first polymeric layer is formed and the thermosetting composition from which the second polymeric layer is formed can be the same or different thermosetting composition.
In one embodiment of the present invention, both the first polymeric layer and the second polymeric layer are formed from a thermosetting composition. In another embodiment, the thermosetting composition comprises a curable coating composition as described below.
As used herein, by xe2x80x9cthermosetting compositionxe2x80x9d is meant one which xe2x80x9csetsxe2x80x9d irreversibly upon curing or crosslinking, wherein the polymer chains of the polymeric components are joined together by covalent bonds. This property is usually associated with a cross-linking reaction of the composition constituents often induced by heat or radiation. Hawley, Gessner G., The Condensed Chemical Dictionary, Ninth Edition., page 856; Surface Coatings, vol. 2, Oil and Colour Chemists"" Association, Australia, TAFE Educational Books (1974). Once cured or crosslinked, a thermosetting composition will not melt upon the application of heat and is insoluble in solvents. By contrast, a xe2x80x9cthermoplastic compositionxe2x80x9d comprises polymeric components which are not joined by covalent bonds and thereby can undergo liquid flow upon heating and are soluble in solvents. Saunders, K. J., Organic Polymer Chemistry, pp. 41-42, Chapman and Hall, London (1973).
In one embodiment of the present invention, the substrate can comprise a metallic substrate. Examples of suitable metallic substrates can include ferrous metals and non-ferrous metals. Suitable ferrous metals include iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold-rolled steel, galvanized (zinc coated) steel, electrogalvanized steel, stainless steel, pickled steel, GALVANNEAL(copyright), GALVALUME(copyright), and GALVAN(copyright) zinc-aluminum alloys coated upon steel, and combinations thereof. Useful non-ferrous metals include aluminum, zinc, magnesium and alloys thereof. Combinations or composites of ferrous and non-ferrous metals can also be used.
In another embodiment of the present invention, the substrate can comprise an elastomeric substrate. Suitable elastomeric substrates can include any of the thermoplastic or thermoset synthetic materials well known in the art. Nonlimiting examples of suitable flexible elastomeric substrate materials include polyethylene, polypropylene, thermoplastic polyolefin (xe2x80x9cTPOxe2x80x9d), reaction injected molded polyurethane (xe2x80x9cRIMxe2x80x9d) and thermoplastic polyurethane (xe2x80x9cTPUxe2x80x9d).
Nonlimiting examples of thermoset materials useful as substrates in connection with the present invention include polyesters, epoxides, phenolics, polyurethanes such as xe2x80x9cRIMxe2x80x9d thermoset materials, and mixtures of any of the foregoing. Nonlimiting examples of suitable thermoplastic materials include thermoplastic polyolefins such as polyethylene, polypropylene, polyamides such as nylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylic polymers, vinyl polymers, polycarbonates, acrylonitrile-butadiene-styrene (xe2x80x9cABSxe2x80x9d) copolymers, ethylene propylene diene terpolymer (xe2x80x9cEPDMxe2x80x9d) rubber, copolymers, and mixtures of any of the foregoing.
If desired, the polymeric substrates described above can have an adhesion promoter present on the surface of the substrate over which any of a number of coating compositions (including the coating compositions of the present invention as described below) can be applied. To facilitate adhesion of organic coatings to polymeric substrates, the substrate can be pretreated using an adhesion promoter layer or tie coat, e.g., a thin layer 0.25 mils (6.35 microns) thick, or by flame or corona pretreatment.
Suitable adhesion promoters for use over polymeric substrates include chlorinated polyolefin adhesion promoters such as are described in U.S. Pat. Nos. 4,997,882; 5,319,032; and 5,397,602, incorporated by reference herein. Other useful adhesion promoting coatings are disclosed in U.S. Pat. No. 6,001,469 (a coating composition containing a saturated polyhydroxylated polydiene polymer having terminal hydroxyl groups), U.S. Pat. No. 5,863,646 (a coating composition having a blend of a saturated polyhydroxylated polydiene polymer and a chlorinated polyolefin) and U.S. Pat. No. 5,135,984 (a coating composition having an adhesion promoting material obtained by reacting a chlorinated polyolefin, maleic acid anhydride, acryl or methacryl modified hydrogenated polybutadiene containing at least one acryloyl group or methacryloyl group per unit molecule, and organic peroxide), which are incorporated herein by reference.
When the substrates are used as components to fabricate automotive vehicles (including, but not limited to, automobiles, trucks and tractors) they can have any shape, and can be selected from the metallic and/or flexible substrates described above. Typical shapes of automotive body components can include body side moldings, fenders, bumpers, hoods, and trim for automotive vehicles.
Also, as mentioned above, in the absence of an adhesion promoting composition, which typically comprises a boron-containing compound, the first polymeric layer and said second polymeric layer have poor interlayer adhesion. That is, the second polymeric layer, in the absence of a boron-containing compound present in either of the first polymeric layer or the second polymeric layer, the two layers have poor interlayer (i.e., intercoat) adhesion. As used herein, by xe2x80x9cpoor interlayer adhesionxe2x80x9d is meant that the second polymeric layer will have delamination or adhesion loss from the first polymeric layer sufficient to be given a rating of 3 or lower, as determined in accordance with ASTM-D 3359-97, method B, using the rating scale specified therein.
The improvement comprises the inclusion of a boron-containing compound in one or both of the first polymeric layer and the second polymeric layer in an amount sufficient to improve the interlayer adhesion of the first polymeric layer and the second polymeric layer. The boron-containing compound can be present in the first polymeric layer only, the second polymeric layer only, or, alternatively, in both the first polymeric layer and the second polymeric layer. In one embodiment of the present invention, the boron-containing compound is present in the first polymeric layer.
Also, it should be understood that the boron-containing compound can be present in any of the polymeric layers comprising the substrate over at least a portion of which is formed the first polymeric layer, as well as any of the polymeric layers that can be subsequently formed over at least a portion of the second polymeric layer.
In the multi-layer composite of the present invention, the boron-containing compound can comprise a compound selected from boric acid, boric acid equivalents, and mixtures thereof.
As used herein, in the specification and in the claims, by xe2x80x9cboric acid equivalentsxe2x80x9d is meant any of the numerous boron-containing compounds which can hydrolyze in aqueous media to form boric acid. As used herein, by xe2x80x9cboric acid equivalentsxe2x80x9d is meant any of the numerous boron-containing compounds which can hydrolyze in aqueous media to form boric acid. Specific, but non-limiting examples of boric acid equivalents include boron oxides, for example, B2O3; boric acid esters such as those obtained by the reaction of boric acid with an alcohol or phenol, for example, trimethyl borate, triethyl borate, tri-n-propyl borate, tri-n-butyl borate, triphenyl borate, triisopropyl borate, tri-t-amyl borate, tri-2-cyclohexylcyclohexyl borate, triethanolamine borate, triisopropylamine borate, and triisopropanolamine borate.
Additionally, amino-containing borates and tertiary amine salts of boric acid may be useful. Such boron-containing compounds include, but are not limited to, 2-(beta-dimethylaminoisopropoxy)-4,5-dimethyl-1,3,2-dioxaborolane, 2-(beta-diethylaminoethoxy)-4,4,6-trimethyl-1,3,2-dioxaborinane, 2-(beta-dimethylaminoethoxy)-4,4,6-trimethyl-1,3,2-dioxaborinane, 2-(betha-diisopropylaminoethoxy-1,3,2-dioxaborinane, 2-(beta-dibutylaminoethoxy)-4-methyl-1,3,2-dioxaborinane, 2-(gamma-dimethylaminopropoxy)-1,3,6,9-tetrapxa-2-boracycloundecane, and 2-(beta-dimethylaminoethoxy)-4,4-(4-hydroxybutyl)-1,3,2-dioxaborolane.
Boric acid equivalents can also include metal salts of boric acid (i.e., metal borates) provided that such metal borates can readily dissociate in aqueous media to form boric acid. Suitable examples of metal borates include, for example, calcium borate, potassium borates such as potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, and potassium octaborate, sodium borates such as sodium perborate, sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium perborate, sodium hexaborate, and sodium octaborate, Likewise, ammonium borates can be useful.
Suitable boric acid equivalents can also include organic oligomeric and polymeric compounds comprising boron-containing moieties. Suitable examples include polymeric borate esters, such as those formed by reacting an active hydrogen-containing polymer, for example, a hydroxyl functional group-containing acrylic polymer or polysiloxane polymer, with boric acid and/or a borate ester to form a polymer having borate ester groups.
Polymers suitable for this purpose can include any of a variety of active hydrogen-containing polymers such as those selected from at least one of acrylic polymers, polyester polymers, polyurethane polymers, polyether polymers and silicon-based polymers. As used herein, by xe2x80x9csilicon-based polymersxe2x80x9d is meant a polymer comprising one or more xe2x80x94SiOxe2x80x94 units in the backbone. Such silicon-based polymers can include hybrid polymers, such as those comprising organic polymeric blocks with one or more xe2x80x94SiOxe2x80x94 units in the backbone.
Examples of active hydrogen-containing polymers suitable for this purpose include polymers comprising functional groups selected from at least one of a hydroxyl group, an amine group, an epoxy group, a carbamate group, a urea group, and a carboxylic acid group. In a particular embodiment of the present invention, the boron-containing compound is formed by reacting boric acid and/or a borate ester with at least one polymer selected from an acrylic polyol, a polyester polyol, a polyurethane polyol, a polyether polyol, a polysiloxane polyol and mixtures thereof.
In one embodiment of the present invention, the adhesion promoter composition comprises a boron-containing compound. The boron-containing compound typically comprises a polysiloxane borate ester formed from reactants (A) at least one polysiloxane comprising at least one of the following structural units (I):
R1nR2mSiO(4xe2x88x92nxe2x88x92m)/2xe2x80x83xe2x80x83(I)
wherein each R1, which may be identical or different, represents H, OH, a monovalent hydrocarbon group or a monovalent siloxane group; each R2, which may be identical or different, represents a group comprising at least one reactive functional group, for example, a hydroxyl group, a carboxyl group or an alkoxyl group, wherein m and n fulfill the requirements of 0 less than n less than 4, 0 less than m less than 4 and 2xe2x89xa6(m+n) less than 4; and (B) at least one boron-containing compound selected from at least one of boric acid, a boric acid equivalent, and mixtures thereof.
It should be understood that the xe2x80x9cat least one polysiloxane comprising at least one structural unit (I)xe2x80x9d above is a polymer that contains at least two Si atoms per molecule. As used herein, the term xe2x80x9cpolymerxe2x80x9d in meant to encompass oligomer, and includes without limitation both homopolymers and copolymers. It should also be understood that the at least one polysiloxane can include linear, branched, dendritic or cyclic polysiloxanes.
Moreover, as used herein, xe2x80x9cformed fromxe2x80x9d denotes open, e.g., xe2x80x9ccomprising,xe2x80x9d claim language. As such, it is intended that a composition xe2x80x9cformed fromxe2x80x9d a list of recited components be a composition comprising at least these recited components, and can further comprise other, nonrecited components, during the composition""s formation.
Also, as used herein, the term xe2x80x9creactivexe2x80x9d refers to a functional group that forms a covalent bond with another functional group under conditions sufficient to cure the composition.
As used herein, the phrase xe2x80x9ceach component is differentxe2x80x9d refers to components which do not have the same chemical structure as other components in the composition.
Each of m and n depicted in the at least one structural unit (I) above fulfill the requirements of 0 less than n less than 4, 0 less than m less than 4 and 2xe2x89xa6(m+n) less than 4. When (m+n) is 3, the value represented by n can be 2 and the value represented by m is 1. Likewise, when (m+n) is 2, the value represented by each of n and m is 1.
As used herein, the term xe2x80x9ccurexe2x80x9d as used in connection with a composition, e.g., xe2x80x9ccomposition when cured,xe2x80x9d shall mean that any crosslinkable components of the composition are at least partially crosslinked. In certain embodiments of the present invention, the crosslink density of the crosslinkable components, i.e., the degree of crosslinking, ranges from 5% to 100% of complete crosslinking. In other embodiments, the crosslink density ranges from 35% to 85% of full crosslinking. In other embodiments, the crosslink density ranges from 50% to 85% of full crosslinking. One skilled in the art will understand that the presence and degree of crosslinking, i.e., the crosslink density, can be determined by a variety of methods, such as dynamic mechanical thermal analysis (DMTA) using a TA Instruments DMA 2980 DMTA analyzer conducted under nitrogen. This method determines the glass transition temperature and crosslink density of free films of coatings or polymers. These physical properties of a cured material are related to the structure of the crosslinked network.
As used herein, a xe2x80x9cmonovalent hydrocarbon groupxe2x80x9d means a monovalent group having a backbone repeat unit based exclusively on carbon. As used herein, xe2x80x9cmonovalentxe2x80x9d refers to a substituent group that, as a substituent group, forms only one single, covalent bond. For example, a monovalent group on the at least one polysiloxane will form one single covalent bond to a silicon atom in the backbone of the at least one polysiloxane polymer. As used herein, xe2x80x9chydrocarbon groupsxe2x80x9d are intended to encompass both branched and unbranched hydrocarbon groups.
Thus, when referring to a xe2x80x9cmonovalent hydrocarbon group,xe2x80x9d the hydrocarbon group can be branched or unbranched, acyclic or cyclic, saturated or unsaturated, or aromatic, and can contain from 1 to 24 (or in the case of an aromatic group from 3 to 24) carbon atoms. Nonlimiting examples of such hydrocarbon groups include alkyl, alkoxy, aryl, alkaryl, and alkoxyaryl groups. Nonlimiting examples of lower alkyl groups include, for example, methyl, ethyl, propyl, and butyl groups. As used herein, xe2x80x9clower alkylxe2x80x9d refers to alkyl groups having from 1 to 6 carbon atoms. One or more of the hydrogen atoms of the hydrocarbon can be substituted with heteroatoms. As used herein, xe2x80x9cheteroatomsxe2x80x9d means elements other than carbon, for example, oxygen, nitrogen, and halogen atoms.
As used herein, xe2x80x9csiloxanexe2x80x9d means a group comprising a backbone comprising two or more xe2x80x94SiOxe2x80x94 groups. For example, the siloxane groups represented by R1, which is discussed above, and R, which is discussed below, can be branched or unbranched, and linear or cyclic. The siloxane groups can be substituted with pendant organic substituent groups, for example, alkyl, aryl, and alkaryl groups. The organic substituent groups can be substituted with heteroatoms, for example, oxygen, nitrogen, and halogen atoms, reactive functional groups, for example, those reactive functional groups discussed above with reference to R2, and mixtures of any of the foregoing.
In one embodiment, the at least one polysiloxane (A), which is used to form the polysiloxane borate ester, comprises at least two reactive functional groups. The at least one polysiloxane can have a reactive group equivalent weight ranging from 50 to 1000 mg per gram of the at least one polysiloxane. In one embodiment, the at least one polysiloxane has a hydroxyl group equivalent weight ranging from 50 to 1000 mg KOH per gram of the at least one polysiloxane. In another embodiment, the at least one polysiloxane has a hydroxyl group equivalent weight ranging from 100 to 300 mg KOH per gram of the at least one polysiloxane, while in another embodiment, the hydroxyl group equivalent weight ranges from 100 to 500 mg KOH per gram.
In another embodiment, R2 (see structural unit l above), which may be identical or different, represents a group comprising at least one reactive functional group selected from a hydroxyl group, a carboxyl group, an isocyanate group, a blocked isocyanate group, a primary amine group, a secondary amine group, an amide group, a carbamate group, a urea group, a urethane group, a vinyl group, an unsaturated ester group such as an acrylate group and a methacrylate group, a maleimide group, a fumarate group, an onium salt group such as a sulfonium group and an ammonium group, an anhydride group, a hydroxy alkylamide group, and an epoxy group.
In another embodiment, the at least one R2 group represents a group comprising at least one reactive functional group selected from a hydroxyl group and a carbamate group. In yet another embodiment, the at least one R2 group represents a group comprising at least two reactive functional groups selected from a hydroxyl group and a carbamate group. In another embodiment, the at least one R2 group represents a group comprising an oxyalkylene group and at least two hydroxyl groups.
In one embodiment, the at least one polysiloxane (A), which is used to form the polysiloxane borate ester, has the following structure (II) or (III): 
wherein: m has a value of at least 1; mxe2x80x2 ranges from 0 to 75; n ranges from 0 to 75; nxe2x80x2 ranges from 0 to 75; each R, which may be identical or different, is selected from H, OH, a monovalent hydrocarbon group, a monovalent siloxane group, and mixtures of any of the foregoing; and xe2x80x94Ra comprises the following structure (IV):
xe2x80x94R3xe2x80x94Xxe2x80x83xe2x80x83(IV)
wherein xe2x80x94R3 is selected from an alkylene group, an oxyalkylene group, an alkylene aryl group, an alkenylene group, an oxyalkenylene group, and an alkenylene aryl group; and X represents a group which comprises at least one reactive functional group selected from a hydroxyl group, a carboxyl group, an isocyanate group, a blocked isocyanate group, a primary amine group, a secondary amine group, an amide group, a carbamate group, a urea group, a urethane group, a vinyl group, an unsaturated ester group such as an acrylate group and a methacrylate group, a maleimide group, a fumarate group, an onium salt group such as a sulfonium group and an ammonium group, an anhydride group, a hydroxy alkylamide group, and an epoxy group.
In one embodiment of the present invention, X represents a group which comprises at least one reactive functional group selected from a hydroxyl group, a carboxyl group, a primary amine group, a secondary amine group, an amide group, a carbamate group, a urea group, an anhydride group, a hydroxy alkylamide group, and an epoxy group.
As used herein, xe2x80x9calkylenexe2x80x9d refers to an acyclic or cyclic, saturated hydrocarbon group having a carbon chain length of from C2 to C25. Nonlimiting examples of suitable alkylene groups include, but are not limited to, those derived from propenyl, 1-butenyl, 1-pentenyl, 1-decenyl, and 1-heneicosenyl, such as, for example (CH2)3, (CH2)4, (CH2)5, (CH2)10, and (CH2)23, respectively, as well as isoprene and myrcene.
As used herein, xe2x80x9coxyalkylenexe2x80x9d refers to an alkylene group containing at least one oxygen atom bonded to, and interposed between, two carbon atoms and having an alkylene carbon chain length of from C2 to C25. Nonlimiting examples of suitable oxyalkylene groups include those derived from trimethylolpropane monoallyl ether, trimethylolpropane diallyl ether, pentaerythritol monoallyl ether, polyethoxylated allyl alcohol, and polypropoxylated allyl alcohol, such as xe2x80x94(CH2)3OCH2C(CH2OH)2(CH2CH2xe2x80x94).
As used herein, xe2x80x9calkylene arylxe2x80x9d refers to an acyclic alkylene group substituted with at least one aryl group, for example, phenyl, and having an alkylene carbon chain length of C2 to C25. The aryl group can be further substituted, if desired. Nonlimiting examples of suitable substituent groups for the aryl group include, but are not limited to, hydroxyl groups, benzyl groups, carboxylic acid groups, and aliphatic hydrocarbon groups. Nonlimiting examples of suitable alkylene aryl groups include, but are not limited to, those derived from styrene and 3-isopropenyl-,-dimethylbenzyl isocyanate, such as xe2x80x94(CH2)2C6H4xe2x80x94 and xe2x80x94CH2CH(CH3)C6H3(C(CH3)2(NCO). As used herein, xe2x80x9calkenylenexe2x80x9d refers to an acyclic or cyclic hydrocarbon group having one or more double bonds and having an alkenylene carbon chain length of C2 to C25. Nonlimiting examples of suitable alkenylene groups include those derived from propargyl alcohol and acetylenic diols, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol which is commercially available from Air Products and Chemicals, Inc. of Allentown, Pa. as SURFYNOL 104.
Formulae (II) and (III) are diagrammatic, and are not intended to imply that the parenthetical portions are necessarily blocks, although blocks may be used where desired. In some cases the polysiloxane may comprise a variety of siloxane units. This is increasingly true as the number of siloxane units employed increases and especially true when mixtures of a number of different siloxane units are used. In those instances where a plurality of siloxane units are used and it is desired to form blocks, oligomers can be formed which can be joined to form the block compound. By judicious choice of reactants, compounds having an alternating structure or blocks of alternating structure may be used.
In one embodiment of the present invention the substituent R3 represents an oxyalkylene group. In another embodiment, R3 represents an oxyalkylene group, and X represents a group which comprises at least two reactive functional groups.
In another embodiment of the present invention where the at least one polysiloxane (A) has the structure (II) or (III) described above, (n+m) ranges from 2 to 9. In yet another embodiment where the at least one polysiloxane have the structure (II) or (III) described above, (n+m) ranges from 2 to 3. In another embodiment, where the at least one polysiloxane have the structure (II) or (III) described above, (nxe2x80x2+mxe2x80x2) ranges from 2 to 9. In another embodiment where the at least one polysiloxane has the structure (II) or (III) described above, (nxe2x80x2+mxe2x80x2) ranges from 2 to 3.
In yet another embodiment of the present invention, the substituent X represents a group comprising at least one reactive functional group selected from a hydroxyl group and a carbamate group. In another embodiment, the substituent X represents a group which comprises at least two hydroxyl groups. In yet another embodiment, X represents a group which comprises at least one group selected from H, a monohydroxy-substituted organic group, and a group having the following structure (V):
R4xe2x80x94(xe2x80x94CH2xe2x80x94OH)pxe2x80x83xe2x80x83(V)
wherein the substituent group R4 represents xe2x80x94CH2xe2x80x94Cxe2x80x94R3 when p is 2 and the substituent group R3 represents a C1 to C4 alkylene group, or the substituent group R4 represents xe2x80x94CH2xe2x80x94Cxe2x80x94 when p is 3, wherein at least a portion of X represents a group having the structure (V). In another embodiment, where the polysiloxane (A) has the structure (I) or (II) described above, m is 2 and p is 2.
In another embodiment of the present invention, the polysiloxane (A) is formed from at least the following reactants: (i) at least one polysiloxane of the formula (VI): 
wherein each substituent group R, which may be identical or different, represents a group selected from H, OH, a monovalent hydrocarbon group, a monovalent siloxane group, and mixtures of any of the foregoing; at least one of the groups represented by R is H, and nxe2x80x2 ranges from 0 to 100, also can range from 0 to 10, and can further range from 0 to 5, such that the percent of SiH content of the polysiloxane ranges from 2 to 50 percent, and can range from 5 to 25 percent; and (ii) at least one molecule which comprises at least functional group selected from a hydroxyl group, a carboxyl group, an isocyanate group, a blocked isocyanate group, a primary amine group, a secondary amine group, an amide group, a carbamate group, a urea group, a urethane group, a vinyl group, an unsaturated ester group such as an acrylate group and a methacrylate group, a maleimide group, a fumarate group, an onium salt group such as a sulfonium group and an ammonium group, an anhydride group, a hydroxy alkylamide group, and an epoxy group and at least one unsaturated bond capable of undergoing a hydrosilylation reaction. In another embodiment, the at least one functional group comprises hydroxyl groups.
It should be appreciated that the various R groups can be the same or different, and, in certain embodiments, the R groups will be entirely monovalent hydrocarbon groups or will be a mixture of different groups such as, for example, monovalent hydrocarbon groups and hydroxyl groups.
In another embodiment, this reaction product is ungelled. As used herein, xe2x80x9cungelledxe2x80x9d refers to a reaction product that is substantially free of crosslinking and has an intrinsic viscosity when dissolved in a suitable solvent, as determined, for example, in accordance with ASTM-D1795 or ASTM-D4243. The intrinsic viscosity of the reaction product is an indication of its molecular weight. A gelled reaction product, on the other hand, since it is of an extremely high molecular weight, will have an intrinsic viscosity too high to measure. As used herein, a reaction product that is xe2x80x9csubstantially free of crosslinkingxe2x80x9d refers to a reaction product that has a weight average molecular weight (Mw), as determined by gel permeation chromatography, of less than 1,000,000.
It also should be noted that the level of unsaturation contained in reactant (ii) above, can be selected to obtain an ungelled reaction product. In other words, when a polysiloxane containing silicon hydride (i) having a higher average value of Sixe2x80x94H functionality is used, reactant (ii) can have a lower level of unsaturation. For example, the polysiloxane containing silicon hydride (i) can be a low molecular weight material where nxe2x80x2 ranges from 0 to 5 and the average value of Sixe2x80x94H functionality is two or less. In this case, reactant (ii) can contain two or more unsaturated bonds capable of undergoing hydrosilylation reaction without the occurrence of gelation.
Nonlimiting examples of polysiloxanes containing silicon hydride (i) include 1,1,3,3-tetramethyl disiloxane where nxe2x80x2 is 0 and the average Sixe2x80x94H functionality is two; and polymethyl polysiloxane containing silicon hydride, where nxe2x80x2 ranges from 4 to 5 and the average Sixe2x80x94H functionality is approximately two, such as is commercially available from BASF Corporation as MASILWAX BASE(copyright).
Materials for use as reactant (ii) above can include hydroxyl functional group-containing allyl ethers such as those selected from trimethylolpropane monoallyl ether, pentaerythritol monoallyl ether, trimethylolpropane diallyl ether, polyoxyalkylene alcohols such as polyethoxylated alcohol, polypropoxylated alcohol, and polybutoxylated alcohol, undecylenic acid-epoxy adducts, allyl glycidyl ether-carboxylic acid adducts, and mixtures of any of the foregoing. Mixtures of hydroxyl functional polyallyl ethers with hydroxyl functional monoallyl ethers or allyl alcohols are suitable as well. In certain instances, reactant (ii) can contain at least one unsaturated bond in a terminal position. Reaction conditions and the ratio of reactants (i) and (ii) are selected so as to form the desired functional group.
The hydroxyl functional group-containing polysiloxane (A) can be prepared by reacting a polysiloxane containing hydroxyl functional groups with an anhydride to form the half-ester acid group under reaction conditions that favor only the reaction of the anhydride and the hydroxyl functional groups, and avoid further esterification from occurring. Nonlimiting examples of suitable anhydrides include hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, phthalic anhydride, trimellitic anhydride, succinic anhydride, chlorendic anhydride, alkenyl succinic anhydride, and substituted alkenyl anhydrides such as octenyl succinic anhydride, and mixtures of any of the foregoing.
The half-ester group-containing reaction product thus prepared can be further reacted with a monoepoxide to form a polysiloxane containing secondary hydroxyl group(s). Nonlimiting examples of suitable monoepoxides are phenyl glycidyl ether, n-butyl glycidyl ether, cresyl glycidyl ether, isopropyl glycidyl ether, glycidyl versatate, for example, CARDURA E available from Shell Chemical Co., and mixtures of any of the foregoing.
In another embodiment of the present invention, the at least one polysiloxane (A) is a carbamate functional group-containing polysiloxane which comprises the reaction product of at least the following reactants:
(i) at least one polysiloxane containing silicon hydride of structure (VI) above where R and nxe2x80x2 are as described above for that structure;
(ii) at least one hydroxyl functional group-containing material having one or more unsaturated bonds capable of undergoing hydrosilylation reaction as described above; and
(iii) at least one low molecular weight carbamate functional material, comprising the reaction product of an alcohol or glycol ether and a urea.
Examples of such xe2x80x9clow molecular weight carbamate functional materialxe2x80x9d include, but are not limited to, alkyl carbamate and hexyl carbamates, and glycol ether carbamates described in U.S. Pat. Nos. 5,922,475 and 5,976,701, which is incorporated herein by reference.
The carbamate functional groups can be incorporated into the polysiloxane by reacting the hydroxyl functional group-containing polysiloxane with the low molecular weight carbamate functional material via a xe2x80x9ctranscarbamoylationxe2x80x9d process. The low molecular weight carbamate functional material, which can be derived from an alcohol or glycol ether, can react with free hydroxyl groups of a polysiloxane polyol, that is, material having an average of two or more hydroxyl groups per molecule, yielding a carbamate functional polysiloxane (A) and the original alcohol or glycol ether. Reaction conditions and the ratio of reactants (i), (ii) and (iii) are selected so as to form the desired groups.
The low molecular weight carbamate functional material can be prepared by reacting the alcohol or glycol ether with urea in the presence of a catalyst such as butyl stannoic acid. Nonlimiting examples of suitable alcohols include lower molecular weight aliphatic, cycloaliphatic and aromatic alcohols, for example, methanol, ethanol, propanol, butanol, cyclohexanol, 2-ethylhexanol, and 3-methylbutanol. Nonlimiting examples of suitable glycol ethers include ethylene glycol methyl ether, and propylene glycol methyl ether. The incorporation of carbamate functional groups into the polysiloxane also can be achieved by reacting isocyanic acid with free hydroxyl groups of the polysiloxane.
As aforementioned, in addition to or in lieu of hydroxyl or carbamate functional groups, the at least one polysiloxane (A) can contain one or more other reactive functional groups such as carboxyl groups, isocyanate groups, blocked isocyanate groups, carboxylate groups, primary or secondary amine groups, amide groups, urea groups, urethane groups, an anhydride group, a hydroxy alkylamide group, epoxy groups, and mixtures of any of the foregoing.
When the at least one polysiloxane (A) contains carboxyl functional groups, the at least one polysiloxane (A) can be prepared by reacting at least one polysiloxane containing hydroxyl functional groups as described above with a polycarboxylic acid or anhydride. Nonlimiting examples of polycarboxylic acids suitable for use include adipic acid, succinic acid, and dodecanedioic acid. Nonlimiting examples of suitable anhydrides include those described above. Reaction conditions and the ratio of reactants are selected so as to form the desired functional groups.
In the case where at least one polysiloxane (A) contains one or more isocyanate functional groups, the at least one polysiloxane can be prepared by reacting at least one polysiloxane containing hydroxyl functional groups, as described above, with a polyisocyanate, such as a diisocyanate. Nonlimiting examples of suitable polyisocyanates include aliphatic polyisocyanates, such as, for example, aliphatic diisocyanates, for example, 1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate; cycloaliphatic polyisocyanates, for example, 1,4-cyclohexyl diisocyanate, isophorone diisocyanate, and xcex1,xcex1-xylylene diisocyanate; and aromatic polyisocyanates, for example, 4,4xe2x80x2-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, and tolylene diisocyanate. These and other suitable polyisocyanates are described in more detail in U.S. Pat. No. 4,046,729, at column 5, line 26 to column 6, line 28, incorporated herein by reference. Reaction conditions and the ratio of reactants are selected so as to form the desired functional groups.
The substituent X in structure (IV) can comprise an oligomeric or polymeric urethane or urea-containing material which is terminated with isocyanate, hydroxyl, primary or secondary amine functional groups, or mixtures of any of the foregoing. When the substituent X comprises such functional groups, the at least one polysiloxane can be the reaction product of at least one polysiloxane polyol as described above, one or more polyisocyanates and, optionally, one or more compounds having at least two active hydrogen atoms per molecule selected from hydroxyl groups, primary amine groups, and secondary amine groups.
Nonlimiting examples of suitable polyisocyanates are those described above. Nonlimiting examples of compounds having at least two active hydrogen atoms per molecule include polyols and polyamines containing primary or secondary amine groups.
Nonlimiting examples of suitable polyols include polyalkylene ether polyols, including thio ethers; polyester polyols, including polyhydroxy polyesteramides; and hydroxyl-containing polycaprolactones and hydroxy-containing acrylic interpolymers. Also useful are polyether polyols formed from the oxyalkylation of various polyols, for example, glycols such as ethylene glycol, 1,6-hexanediol, Bisphenol A, and the like, or higher polyols such as trimethylolpropane, pentaerythritol and the like. Polyester polyols also can be used. These and other suitable polyols are described in U.S. Pat. No. 4,046,729 at column 7, line 52 to column 8, line 9; column 8, line 29 to column 9, line 66; and U.S. Pat. No. 3,919,315 at column 2, line 64 to column 3, line 33, both incorporated herein by reference.
Nonlimiting examples of suitable polyamines include primary or secondary diamines or polyamines in which the groups attached to the nitrogen atoms can be saturated or unsaturated, aliphatic, alicyclic, aromatic, aromatic-substituted-aliphatic, aliphatic-substituted-aromatic and heterocyclic. Exemplary suitable aliphatic and alicyclic diamines include 1,2-ethylene diamine, 1,2-porphylene diamine, 1,8-octane diamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like. Suitable aromatic diamines include phenylene diamines and the toluene diamines, for example, o-phenylene diamine and p-tolylene diamine. These and other suitable polyamines are described in detail in U.S. Pat. No. 4,046,729 at column 6, line 61 to column 7, line 26, incorporated herein by reference.
In one embodiment, the substituent group X of the structure (IV) can comprise a polymeric ester-containing group which is terminated with hydroxyl or carboxylic acid functional groups. When X is such a group, at least one polysiloxane can be the reaction product of one or more polysiloxane polyols as described above, one or more materials comprising at least one carboxylic acid functional group, and one or more organic polyols. Nonlimiting suitable examples of materials comprising at least one carboxylic acid functional group include carboxylic acid group-containing polymers well-known in the art, for example, carboxylic acid group-containing acrylic polymers, polyester polymers, and polyurethane polymers, such as those described in U.S. Pat. No. 4,681,811. Nonlimiting examples of suitable organic polyols include those described above.
To form the at least one polysiloxane (A) containing epoxy groups, at least one polysiloxane containing hydroxyl functional groups as described above can be further reacted with a polyepoxide. The polyepoxide can be an aliphatic or cycloaliphatic polyepoxide or mixtures of any of the foregoing. Nonlimiting examples of polyepoxides suitable for use include epoxy functional acrylic copolymers prepared from at least one ethylenically unsaturated monomer comprising at least one epoxy group, for example glycidyl (meth)acrylate and allyl glycidyl ether, and one or more ethylenically unsaturated monomers which have no epoxy functionality. The preparation of such epoxy functional acrylic copolymers is described in detail in U.S. Pat. No. 4,681,811 at column 4, line 52 to column 5, line 50, incorporated herein by reference. Reaction conditions and the ratio of reactants are selected so as to form the desired functional groups.
In the embodiment of the present invention where the boron-containing compound is formed from the at least one functional group-containing polysiloxane (A) and the boron-containing compound (B), the at least one polysiloxane (A) can be reacted with the boron-containing compound (B) under condensation reaction conditions well known in the art. For example, boron-containing compound can be prepared by mixing boric acid or a boric acid equivalent with a polyol and removing water by distillation either directly or in combination with a solvent. Other methods for preparing boric acid esters can be found in xe2x80x9cKirk-Othmer Encyclopedia of Chemical Technologyxe2x80x9d 4th edition, Vol 4, p 416; John Wiley and sons; 1992
Also, it should be understood, that the boron-containing compound can be formed in situ. That is, the composition from which one or both of the first and second polymeric layers is formed can comprise boric acid and/or a boric acid ester and an active hydrogen-containing component, such as a polymer or polysiloxane comprising hydroxyl functional groups, as separate components. The boron-containing compound can then be formed, for example, by forming the condensate reaction product, i.e., the boric acid ester, within the composition at ambient temperature or as the composition undergoes a curing reaction at elevated temperatures. In this instance, the composition can comprise the condensate reaction product, and the boric acid and/or the borate ester and the active hydrogen-containing component as three separate components.
As mentioned previously, one or both of the first polymeric layer and the second polymeric layer can be formed from a thermosetting composition. In one embodiment of the invention, one or both of the first polymeric layer and the second polymeric layer comprise a cured layer formed from a thermosetting composition comprising (A) at least one film-forming polymer having reactive functional groups; (B) at least one curing agent having functional groups reactive with the functional groups of (A); and (C) at least one of the aforementioned adhesion promoter composition, e.g., one or more boron-containing compounds, wherein the components are different.
When added to the other components that form the thermosetting composition from which the curable composition from which the first and/or the second polymeric layer is formed, the adhesion promoter composition, e.g., a boron-containing compound, (C) can be present in the composition in an amount sufficient to provide an amount of elemental material, e.g., boron, present in the composition of at least 0.001 weight percent, often at least 0.025 weight percent, usually at least 0.05 weight percent, and typically at least 0.10 weight percent, based on total weight of the resin solids present in the composition. Also, the adhesion promoter composition, e.g., a boron-containing compound, (C), when added to the other components that form the thermosetting composition from which the curable composition from which the first and/or second polymeric layer is formed, can be present in the composition in an amount sufficient to provide an amount of elemental material, e.g., boron, present in the composition of less than 5 weight percent, often less than 3 weight percent, usually less than 2.5 weight percent, and typically less than 2 weight percent, based on total weight of the resin solids present in the composition. The amount of adhesion promoter composition (C) is present in the thermosetting composition in an amount sufficient to provide an amount of elemental material present in the composition that can range between any combination of these values inclusive of the recited values.
As aforementioned, the thermosetting composition of the present invention (which can comprise a curable coating composition), comprises, in addition to the compound (C), at least one film-forming polymer comprising at least one reactive functional group (A), and at least one reactant, typically a curing agent, (B) comprising at least one functional group which is reactive with the functional group of (A). The at least one film-forming polymer having reactive functional groups (A) can be different from and in addition to the at least one curing agent (B), and composition/compound (C). The film-forming polymer (A) can have at least one functional group reactive with the curing agent (B), and, if applicable, the compound (C). In one embodiment, the at least one reactive functional group-containing film-forming polymer (A) can be selected from at least one of polyether polymers, polyester polymers, acrylic polymers, silicon-based polymers, polyepoxide polymers, and polyurethane polymers.
In a particular embodiment of the present invention, the film-forming polymer (A) can comprise at least one reactive functional group selected from a hydroxyl group, a carboxyl group, an isocyanate group, a blocked isocyanate group, a primary amine group, a secondary amine group, an amide group, a carbamate group, a urea group, a urethane group, a vinyl group, an unsaturated ester group, a maleimide group, a fumarate group, an anhydride group, a hydroxy alkylamide group, and an epoxy group.
In another embodiment of the present invention, the film-forming polymer (A)comprises at least one reactive functional group selected from a hydroxyl group, a carbamate group, an epoxy group, an isocyanate group, and a carboxyl group. In another embodiment, the polymer comprises at least one reactive functional group selected from a hydroxyl group, and a carbamate group.
The film-forming polymer (A) can comprise a mixture of any of the foregoing reactive functional groups.
Film-forming polymers suitable for use as the at least one reactive functional group-containing film-forming polymer (A) can include any of a variety of functional polymers known in the art. For example, suitable hydroxyl group-containing polymers can include acrylic polyols, polyester polyols, polyurethane polyols, polyether polyols, and mixtures thereof. In a particular embodiment of the present invention, the film-forming polymer is an acrylic polyol having a hydroxyl equivalent weight ranging from 1000 to 100 grams per solid equivalent, preferably 500 to 150 grams per solid equivalent.
Suitable hydroxyl group and/or carboxyl group-containing acrylic polymers can be prepared from polymerizable ethylenically unsaturated monomers and are typically copolymers of (meth)acrylic acid and/or hydroxylalkyl esters of (meth)acrylic acid with one or more other polymerizable ethylenically unsaturated monomers such as alkyl esters of (meth)acrylic acid including methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate and 2-ethyl hexylacrylate, and vinyl aromatic compounds such as styrene, alpha-methyl styrene, and vinyl toluene. As used herein, xe2x80x9c(meth)acrylatexe2x80x9d and like terms is intended to include both acrylates and methacrylates.
In a one embodiment of the present invention the acrylic polymer can be prepared from ethylenically unsaturated, beta-hydroxy ester functional monomers. Such monomers can be derived from the reaction of an ethylenically unsaturated acid functional monomer, such as monocarboxylic acids, for example, acrylic acid, and an epoxy compound which does not participate in the free radical initiated polymerization with the unsaturated acid monomer. Examples of such epoxy compounds include glycidyl ethers and esters. Suitable glycidyl ethers include glycidyl ethers of alcohols and phenols such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether and the like. Suitable glycidyl esters include those which are commercially available from Shell Chemical Company under the tradename CARDURA E; and from Exxon Chemical Company under the tradename GLYDEXX-10. Alternatively, the beta-hydroxy ester functional monomers can be prepared from an ethylenically unsaturated, epoxy functional monomer, for example glycidyl (meth)acrylate and allyl glycidyl ether, and a saturated carboxylic acid, such as a saturated monocarboxylic acid, for example isostearic acid.
Epoxy functional groups can be incorporated into the polymer prepared from polymerizable ethylenically unsaturated monomers by copolymerizing oxirane group-containing monomers, for example glycidyl (meth)acrylate and allyl glycidyl ether, with other polymerizable ethylenically unsaturated monomers, such as those discussed above. Preparation of such epoxy functional acrylic polymers is described in detail in U.S. Pat. No. 4,001,156 at columns 3 to 6, incorporated herein by reference.
Carbamate functional groups can be incorporated into the polymer prepared from polymerizable ethylenically unsaturated monomers by copolymerizing, for example, the above-described ethylenically unsaturated monomers with a carbamate functional vinyl monomer such as a carbamate functional alkyl ester of methacrylic acid. Useful carbamate functional alkyl esters can be prepared by reacting, for example, a hydroxyalkyl carbamate, such as the reaction product of ammonia and ethylene carbonate or propylene carbonate, with methacrylic anhydride. Other useful carbamate functional vinyl monomers include, for instance, the reaction product of hydroxyethyl methacrylate, isophorone diisocyanate, and hydroxypropyl carbamate; or the reaction product of hydroxypropyl methacrylate, isophorone diisocyanate, and methanol. Still other carbamate functional vinyl monomers may be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxyl functional acrylic or methacrylic monomer such as hydroxyethyl acrylate, and those described in U.S. Pat. No. 3,479,328, incorporated herein by reference. Carbamate functional groups can also be incorporated into the acrylic polymer by reacting a hydroxyl functional acrylic polymer with a low molecular weight alkyl carbamate such as methyl carbamate. Pendant carbamate groups can also be incorporated into the acrylic polymer by a xe2x80x9ctranscarbamoylationxe2x80x9d reaction in which a hydroxyl functional acrylic polymer is reacted with a low molecular weight carbamate derived from an alcohol or a glycol ether. The carbamate groups exchange with the hydroxyl groups yielding the carbamate functional acrylic polymer and the original alcohol or glycol ether. Also, hydroxyl functional acrylic polymers can be reacted with isocyanic acid to provide pendent carbamate groups. Likewise, hydroxyl functional acrylic polymers can be reacted with urea to provide pendent carbamate groups.
The polymers prepared from polymerizable ethylenically unsaturated monomers can be prepared by solution polymerization techniques, which are well-known to those skilled in the art, in the presence of suitable catalysts such as organic peroxides or azo compounds, for example, benzoyl peroxide or N,N-azobis(isobutylronitrile). The polymerization can be carried out in an organic solution in which the monomers are soluble by techniques conventional in the art. Alternatively, these polymers can be prepared by aqueous emulsion or dispersion polymerization techniques which are well-known in the art. The ratio of reactants and reaction conditions are selected to result in an acrylic polymer with the desired pendent functionality.
Polyester polymers are also useful in the coating compositions of the invention as the film-forming polymer. Useful polyester polymers typically include the condensation products of polyhydric alcohols and polycarboxylic acids. Suitable polyhydric alcohols can include ethylene glycol, neopentyl glycol, trimethylol propane, and pentaerythritol. Suitable polycarboxylic acids can include adipic acid, 1,4-cyclohexyl dicarboxylic acid, and hexahydrophthalic acid. Besides the polycarboxylic acids mentioned above, functional equivalents of the acids such as anhydrides where they exist or lower alkyl esters of the acids such as the methyl esters can be used. Also, small amounts of monocarboxylic acids such as stearic acid can be used. The ratio of reactants and reaction conditions are selected to result in a polyester polymer with the desired pendent functionality, i.e., carboxyl or hydroxyl functionality.
For example, hydroxyl group-containing polyesters can be prepared by reacting an anhydride of a dicarboxylic acid such as hexahydrophthalic anhydride with a diol such as neopentyl glycol in a 1:2 molar ratio. Where it is desired to enhance air-drying, suitable drying oil fatty acids may be used and include those derived from linseed oil, soya bean oil, tall oil, dehydrated castor oil, or tung oil.
Carbamate functional polyesters can be prepared by first forming a hydroxyalkyl carbamate that can be reacted with the polyacids and polyols used in forming the polyester. Alternatively, terminal carbamate functional groups can be incorporated into the polyester by reacting isocyanic acid with a hydroxy functional polyester. Also, carbamate functionality can be incorporated into the polyester by reacting a hydroxyl polyester with a urea. Additionally, carbamate groups can be incorporated into the polyester by a transcarbamoylation reaction. Preparation of suitable carbamate functional group-containing polyesters are those described in U.S. Pat. No. 5,593,733 at column 2, line 40 to column 4, line 9, incorporated herein by reference.
Polyurethane polymers containing terminal isocyanate or hydroxyl groups also can be used as the polymer (d) in the coating compositions of the invention. The polyurethane polyols or NCO-terminated polyurethanes which can be used are those prepared by reacting polyols including polymeric polyols with polyisocyanates. Polyureas containing terminal isocyanate or primary and/or secondary amine groups which also can be used are those prepared by reacting polyamines including polymeric polyamines with polyisocyanates. The hydroxyl/isocyanate or amine/isocyanate equivalent ratio is adjusted and reaction conditions are selected to obtain the desired terminal groups. Examples of suitable polyisocyanates include those described in U.S. Pat. No. 4,046,729 at column 5, line 26 to column 6, line 28, incorporated herein by reference. Examples of suitable polyols include those described in U.S. Pat. No. 4,046,729 at column 7, line 52 to column 10, line 35, incorporated herein by reference. Examples of suitable polyamines include those described in U.S. Pat. No. 4,046,729 at column 6, line 61 to column 7, line 32 and in U.S. Pat. No. 3,799,854 at column 3, lines 13 to 50, both incorporated herein by reference.
Carbamate functional groups can be introduced into the polyurethane polymers by reacting a polyisocyanate with a polyester having hydroxyl functionality and containing pendent carbamate groups. Alternatively, the polyurethane can be prepared by reacting a polyisocyanate with a polyester polyol and a hydroxyalkyl carbamate or isocyanic acid as separate reactants. Examples of suitable polyisocyanates are aromatic isocyanates, such as 4,4xe2x80x2-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate and toluene diisocyanate, and aliphatic polyisocyanates, such as 1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate. Cycloaliphatic diisocyanates, such as 1,4-cyclohexyl diisocyanate and isophorone diisocyanate also can be employed.
Examples of suitable polyether polyols include polyalkylene ether polyols such as those having the following structural formulas (VII) or (VIII): 
or 
wherein the substituent R is hydrogen or a lower alkyl group containing from 1 to 5 carbon atoms including mixed substituents, and n has a value typically ranging from 2 to 6 and m has a value ranging from 8 to 100 or higher. Exemplary polyalkylene ether polyols include poly(oxytetramethylene) glycols, poly(oxytetraethylene) glycols, poly(oxy-1,2-propylene) glycols, and poly(oxy-1,2-butylene) glycols.
Also useful are polyether polyols formed from oxyalkylation of various polyols, for example, glycols such as ethylene glycol, 1,6-hexanediol, Bisphenol A, and the like, or other higher polyols such as trimethylolpropane, pentaerythritol, and the like. Polyols of higher functionality which can be utilized as indicated can be made, for instance, by oxyalkylation of compounds such as sucrose or sorbitol. One commonly utilized oxyalkylation method is reaction of a polyol with an alkylene oxide, for example, propylene or ethylene oxide, in the presence of an acidic or basic catalyst. Specific examples of polyethers include those sold under the names TERATHANE and TERACOL, available from E. I. Du Pont de Nemours and Company, Inc.
Generally, the polymers having reactive functional groups which are useful in the coating compositions of the invention have a weight average molecular weight (Mw) typically ranging from 1000 to 20,000 preferably 1500 to 15,000 and more preferably 2000 to 12,000 as determined by gel permeation chromatography using a polystyrene standard.
Hydroxyl and/or carbamate functional group-containing polymers are typically employed.
Polyepoxides such as those described below with reference to the curing agent (B), can also be used.
The polymer having reactive functional groups (A) can be present in the thermosetting compositions in an amount of at least 2 percent by weight, usually at least 5 percent by weight, and typically at least 10 percent by weight based on weight of total resin solids in the coating composition. Also, the polymer having reactive functional groups can be present in the thermosetting compositions of the invention in an amount less than 80 percent by weight, usually less than 60 percent by weight, and typically less than 50 percent by weight based on weight of total resin solids in the coating composition. The amount of the polymer (A) having reactive functional groups present in the thermosetting compositions of the present invention can range between any combination of these values inclusive of the recited values.
As aforementioned, in addition to the functional group-containing film-forming polymer (A) and the boron-containing compound (C), the thermosetting composition of the present invention further comprises at least one curing agent having functional groups reactive with the functional groups of the film-forming polymer (A) (and/or the boron-containing compound (C), where applicable).
Dependent upon the reactive functional groups of the film-forming polymer (A)(and, optionally, the boron-containing compound (C)), this curing agent can be selected from an aminoplast resin, a polyisocyanate, a blocked isocyanate, a polyepoxide, a polyacid, an anhydride, an amine, a polyol, and mixtures of any of the foregoing. In one embodiment, the at least one curing agent (B) is selected from an aminoplast resin and a polyisocyanate.
In another embodiment, the present invention is directed to any composition as previously described wherein the curing agent comprises an aminoplast resin. Aminoplast resins, which can comprise phenoplasts, as curing agents for hydroxyl, carboxylic acid, and carbamate functional group-containing materials are well known in the art. Suitable aminoplast resins, such as, for example, those discussed above, are known to those of ordinary skill in the art. Aminoplasts can be obtained from the condensation reaction of formaldehyde with an amine or amide. Nonlimiting examples of amines or amides include melamine, urea, or benzoguanamine. Condensates with other amines or amides can be used; for example, aldehyde condensates of glycoluril, which give a high melting crystalline product useful in powder coatings. While the aldehyde used is most often formaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehyde can be used.
The aminoplast resin contains imino and methylol groups and in certain instances at least a portion of the methylol groups are etherified with an alcohol to modify the cure response. Any monohydric alcohol can be employed for this purpose including methanol, ethanol, n-butyl alcohol, isobutanol, and hexanol.
Nonlimiting examples of aminoplasts include melamine-, urea-, or benzoguanamine-formaldehyde condensates, in certain instances monomeric and at least partially etherified with one or more alcohols containing from one to four carbon atoms. Nonlimiting examples of suitable aminoplast resins are commercially available, for example, from Cytec Industries, Inc. under the trademark CYMEL(copyright) and from Solutia, Inc. under the trademark RESIMENE(copyright).
In another embodiment of the present invention, the curing agent comprises an aminoplast resin which, when added to the other components that form the thermosetting composition, is generally present in an amount ranging from 2 weight percent to 65 weight percent, can be present in an amount ranging from 5 weight percent to 50 weight percent, and typically is present in an amount ranging from 5 weight percent to 40 weight percent based on total weight of resin solids present in the composition.
In yet another embodiment of the present invention, the at least one reactant (B) comprises a polyisocyanate curing agent. As used herein, the term xe2x80x9cpolyisocyanatexe2x80x9d is intended to include blocked (or capped) isocyanates as well as unblocked (poly)isocyanates. The polyisocyanate can be an aliphatic or an aromatic polyisocyanate, or a mixture of the foregoing two. Diisocyanates can be used, although higher polyisocyanates such as isocyanurates of diisocyanates are often used. Higher polyisocyanates also can be used in combination with diisocyanates. Isocyanate prepolymers, for example, reaction products of polyisocyanates with polyols also can be used. Mixtures of polyisocyanate curing agents can be used.
If the polyisocyanate is blocked or capped, any suitable aliphatic, cycloaliphatic, or aromatic alkyl monoalcohol known to those skilled in the art can be used as a capping agent for the polyisocyanate. Other suitable capping agents include oximes and lactams. When used, the polyisocyanate curing agent is typically present, when added to the other components which form the coating composition, in an amount ranging from 5 to 65 weight percent, can be present in an amount ranging from 10 to 45 weight percent, and often are present in an amount ranging from 15 to 40 percent by weight based on the total weight of resin solids present in the composition.
Other useful curing agents comprise blocked isocyanate compounds such as, for example, the tricarbamoyl triazine compounds described in detail in U.S. Pat. No. 5,084,541, which is incorporated by reference herein. When used, the blocked polyisocyanate curing agent can be present, when added to the other components in the composition, in an amount ranging up to 20 weight percent, and can be present in an amount ranging from 1 to 20 weight percent, based on the total weight of resin solids present in the composition.
In one embodiment of the present invention, the curing agent comprises both an aminoplast resin and a polyisocyanate.
Anhydrides as curing agents for hydroxyl functional group-containing materials also are well known in the art and can be used in the present invention. Nonlimiting examples of anhydrides suitable for use as curing agents in the compositions of the invention include those having at least two carboxylic acid anhydride groups per molecule which are derived from a mixture of monomers comprising an ethylenically unsaturated carboxylic acid anhydride and at least one vinyl co-monomer, for example, styrene, alpha-methyl styrene, vinyl toluene, and the like. Nonlimiting examples of suitable ethylenically unsaturated carboxylic acid anhydrides include maleic anhydride, citraconic anhydride, and itaconic anhydride. Alternatively, the anhydride can be an anhydride adduct of a diene polymer such as maleinized polybutadiene or a maleinized copolymer of butadiene, for example, a butadiene/styrene copolymer. These and other suitable anhydride curing agents are described in U.S. Pat. No. 4,798,746 at column 10, lines 16-50; and in U.S. Pat. No. 4,732,790 at column 3, lines 41-57, both of which are incorporated herein by reference.
Polyepoxides as curing agents for carboxylic acid functional group-containing materials are well known in the art. Nonlimiting examples of polyepoxides suitable for use in the compositions of the present invention comprise polyglycidyl esters (such as acrylics from glycidyl methacrylate), polyglycidyl ethers of polyhydric phenols and of aliphatic alcohols, which can be prepared by etherification of the polyhydric phenol, or aliphatic alcohol with an epihalohydrin such as epichlorohydrin in the presence of alkali. These and other suitable polyepoxides are described in U.S. Pat. No. 4,681,811 at column 5, lines 33 to 58, which is incorporated herein by reference.
Suitable curing agents for epoxy functional group-containing materials comprise polyacid curing agents, such as the acid group-containing acrylic polymers prepared from an ethylenically unsaturated monomer containing at least one carboxylic acid group and at least one ethylenically unsaturated monomer which is free from carboxylic acid groups. Such acid functional acrylic polymers can have an acid number ranging from 30 to 150. Acid functional group-containing polyesters can be used as well. The above-described polyacid curing agents are described in further detail in U.S. Pat. No. 4,681,811 at column 6, line 45 to column 9, line 54, which is incorporated herein by reference.
Also well known in the art as curing agents for isocyanate functional group-containing materials are polyols, that is, materials having two or more hydroxyl groups per molecule, different from component (b) when component (b) is a polyol. Nonlimiting examples of such materials suitable for use in the compositions of the invention include polyalkylene ether polyols, including thio ethers; polyester polyols, including polyhydroxy polyesteramides; and hydroxyl-containing polycaprolactones and hydroxy-containing acrylic copolymers. Also useful are polyether polyols formed from the oxyalkylation of various polyols, for example, glycols such as ethylene glycol, 1,6-hexanediol, Bisphenol A and the like, or higher polyols such as trimethylolpropane, pentaerythritol, and the like. Polyester polyols also can be used. These and other suitable polyol curing agents are described in U.S. Pat. No. 4,046,729 at column 7, line 52 to column 8, line 9; column 8, line 29 to column 9, line 66; and U.S. Pat. No. 3,919,315 at column 2, line 64 to column 3, line 33, both of which are incorporated herein by reference.
Polyamines also can be used as curing agents for isocyanate functional group-containing materials. Nonlimiting examples of suitable polyamine curing agents include primary or secondary diamines or polyamines in which the radicals attached to the nitrogen atoms can be saturated or unsaturated, aliphatic, alicyclic, aromatic, aromatic-substituted-aliphatic, aliphatic-substituted-aromatic, and heterocyclic. Nonlimiting examples of suitable aliphatic and alicyclic diamines include 1,2-ethylene diamine, 1,2-porphylene diamine, 1,8-octane diamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like. Nonlimiting examples of suitable aromatic diamines include phenylene diamines and the toluene diamines, for example, o-phenylene diamine and p-tolylene diamine. These and other suitable polyamines described in detail in U.S. Pat. No. 4,046,729 at column 6, line 61 to column 7, line 26, which is incorporated herein by reference.
When desired, appropriate mixtures of curing agents may be used. It should be mentioned that the thermosetting compositions can be formulated as a one-component composition where a curing agent such as an aminoplast resin and/or a blocked isocyanate compound such as those described above is admixed with other composition components. The one-component composition can be storage stable as formulated. Alternatively, compositions can be formulated as a two-component composition where a polyisocyanate curing agent such as those described above can be added to a pre-formed admixture of the other composition components just prior to application. The pre-formed admixture can comprise curing agents such as aminoplast resins and/or blocked isocyanate compounds such as those described above.
In another embodiment in which the thermosetting composition can form a coating which is cured by actinic radiation or the combination of actinic radiation and thermal energy, the components from which the coating composition are formed further can comprise at least one photoinitiator or photosensitizer which provides free radicals or cations to initiate the polymerization process. Useful photoinitiators have an adsorption in the range of 150 to 2,000 nm. Non-limiting examples of useful photoinitiators include benzoin, benzophenone, hydroxy benzophenone, anthraquinone, thioxanthone, substituted benzoins such as butyl isomers of benzoin ethers, xcex1,xcex1-diethoxyacetophenone, xcex1,xcex1-dimethoxy-xcex1-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl propane 1-one and 2,4,6-trimethyl benzoyl diphenyl phosphine oxide.
In one embodiment, the present invention is directed to an improved curable coating composition used to form a multi-layer composite coating comprising at least a first coating layer formed on at least a portion of a substrate, and a second coating layer formed over at least a portion of the first coating layer, where one or both the first coating layer and the second coating layer are formed from the curable coating composition, and wherein in the absence of a boron-containing compound, the first and second coating layers have poor interlayer adhesion. The improvement comprises the inclusion in the curable coating composition of a boron-containing compound present in an amount sufficient to improve the interlayer adhesion between the first coating layer and the second coating layer.
The curable coating composition of the present invention can comprise any of the foregoing thermosetting compositions described above. Also, in the multi-layer composite coating wherein both of the first and second coating layers are formed from the curable composition, it should be understood that each of the first and second coating layers can be formed from the same or different curable coating compositions.
In a particular embodiment, the present invention is directed to a multi-layer composite coating as discussed above where one or both of the first coating layer and the second coating layer are formed from a curable coating composition formed from components comprising (A) an acrylic and/or a polyester polymer having at least one reactive functional group selected from a hydroxyl group, a carbamate group, and mixtures thereof; such as any of those described above, (B) a curing agent selected from an aminoplast resin and a polyisocyanate, such as those described above, and (C) any of the foregoing boron-containing compounds described above. In another embodiment, the present invention is directed to a multi-layer composite coating as discussed above where one or both of the first coating layer and the second coating layer are formed from a curable coating composition formed from components comprising (A) an acrylic and/or a polyester polymer having at least one reactive functional group selected from a hydroxyl group, a carbamate group, and mixtures thereof; (B) a curing agent selected from an aminoplast resin and a blocked isocyanate comprising a tricarbamoyl triazine; and (C) any of the boron-containing compounds described above.
The curable coating compositions of the present invention can be solvent-based compositions, water-based compositions, in solid particulate form, that is, a powder composition, in the form of a powder slurry or an aqueous dispersion. The components of the present invention used to form the compositions of the present invention can be dissolved or dispersed in an organic solvent. Nonlimiting examples of suitable organic solvents include alcohols, such as butanol; ketones, such as methyl amyl ketone; aromatic hydrocarbons, such as xylene; and glycol ethers, such as, ethylene glycol monobutyl ether; esters; other solvents; and mixtures of any of the foregoing.
In solvent based compositions, the organic solvent is generally present in amounts ranging from 5 to 80 percent by weight based on total weight of the resin solids of the components which form the composition, and can be present in an amount ranging from 30 to 50 percent by weight. The compositions as described above can have a total solids content ranging from 40 to 75 percent by weight based on total weight of the resin solids of the components which form the composition, and can have a total solids content ranging from 50 to 70 percent by weight. Alternatively, the inventive compositions can be in solid particulate form suitable for use as a powder coating, or suitable for dispersion in a liquid medium such as water for use as a powder slurry.
In a further embodiment, the compositions as previously described further comprise a catalyst which is present during the composition""s formation. In one embodiment, the catalyst is present in an amount sufficient to accelerate the reaction between at least one reactive functional group of the at least one curing agent and/or at least one reactive functional group of the at least one film-forming polymer.
Nonlimiting examples of suitable catalysts include acidic materials, for example, acid phosphates, such as phenyl acid phosphate, and substituted or unsubstituted sulfonic acids such as dodecylbenzene sulfonic acid or para-toluene sulfonic acid. Non-limiting examples of suitable catalysts for reactions between isocyanate groups and active hydrogen-containing materials, for example, those comprising hydroxyl groups, include tin catalysts such as dibutyl tin dilaurate and dibutyl tin oxide. Non-limiting examples of epoxy acid base catalysts include tertiary amines such as N,Nxe2x80x2-dimethyldodecyl amine catalysts. In another embodiment, the catalyst can be a phosphatized polyester or a phosphatized epoxy. In this embodiment, the catalyst can be, for example, the reaction product of phosphoric acid and a bisphenol A diglycidyl ether having two hydrogenated phenolic rings, such as DRH-151, which is commercially available from Shell Chemical Co. The catalyst can be present, when added to the other components that form the composition, in an amount ranging from 0.1 to 5.0 percent by weight, and is typically present in an amount ranging from 0.5 to 1.5 percent by weight based on the total weight of resin solids present in the composition.
In another embodiment, additional components can be present during the formation of the compositions as previously described. These additional components include, but are not limited to, particles different from components (A), (B) and (C), for example, silica in colloidal, fumed, or amorphous form, alumina or colloidal alumina, titanium dioxide, cesium oxide, yttrium oxide, colloidal yttria, zirconia, e.g., colloidal or amorphous zirconia, and mixtures of any of the foregoing, flexibilizers, plasticizers, surface active agents, thixotropic agents, rheology control modifiers, anti-gassing agents, organic cosolvents, flow controllers, hindered amine light stabilizers, anti-oxidants, UV light absorbers, coloring agents or tints, and similar additives conventional in the art, as well as mixtures of any of the foregoing can be included in the composition. These additional ingredients can be present, when added to the other components that form the composition, in an amount up to 40 percent by weight based on the total weight of resin solids present in the composition.
In one embodiment, the present invention is directed to a multi-layer composite coating wherein the first curable coating composition comprises a base coating composition and the second curable composition comprises a top coating composition. In another embodiment of the present invention, the base coating composition comprises a substantially pigment-free coating composition and the top coating composition comprises a substantially pigment-free top coating composition. In an alternative embodiment of the present invention, the base coating composition comprises a pigment-containing coating composition and the top coating composition comprises a pigment-containing composition. In another embodiment of the present invention, the base coating composition comprises a pigment-containing coating composition and the top coating composition comprises a substantially pigment-free coating composition. In another embodiment of the present invention, the base coating composition comprises a substantially pigment-free base coating composition and the top coating composition comprises a pigment-containing coating composition.
As used herein, by xe2x80x9csubstantially pigment-free coating compositionxe2x80x9d is meant a coating composition which forms a transparent coating, such as a clearcoat in a multi-component composite coating composition. Such compositions are sufficiently free of pigment or particles such that the optical properties of the resultant coatings are not seriously compromised. As used herein, xe2x80x9ctransparentxe2x80x9d means that the cured coating has a BYK Haze index of less than 50 as measured using a BYK/Haze Gloss instrument.
The pigment-containing coating compositions can any of the pigmented compositions commonly used in the coatings industry. For example, the pigment-containing coating composition can comprise a primer coating composition, such as a pigmented thermosetting weldable primer coating composition, for example, those commercially available under the tradename BONAZINC(copyright), an electrodepositable coating composition such as ED-5000, a primer-surfacer coating composition such as GPX45379, a color-enhancing base coat such as HWB-9517, and ODCT6373, all available from PPG Industries, Inc. of Pittsburgh, Pa. or an adhesive composition such as those used as automotive windshield adhesives, for example, BETASEAL 15625, available from Essex Specialty Products.
Likewise, the pigment-free curable coating composition can comprise any of the pigment-free coatings known in the art such as those used as clear coats in color-plus-clear coating systems for the automotive industry. Non-limiting examples include TKU-1050AR, ODCT8000, and those available under the tradenames DIAMOND COAT(copyright) and NCT(copyright), all commercially available from PPG Industries, Inc.
In another embodiment, the present invention is directed to multi-component composite coating compositions comprising a basecoat deposited from a pigment-containing base coating composition, which can comprise any of the aforementioned curable coating compositions, and a topcoat deposited from any of the coating compositions of the present invention previously described above. In one embodiment, the present invention is directed to a multi-component composite coating composition as previously described, wherein the topcoating composition is transparent after curing and is selected from any of the compositions previously described. The components used to form the topcoating composition in these embodiments can be selected from the coating components discussed above, and additional components also can be selected from those recited above. It should be understood that one or both of the base coating composition and the top coating composition can be formed from the curable coating compositions of the present invention.
The basecoat and transparent topcoat (i.e., clearcoat) compositions used in the multi-component composite coating compositions of the present invention in certain instances can be formulated into liquid high solids coating compositions, that is, compositions containing 40 percent, or greater than 50 percent by weight resin solids. The solids content can be determined by heating a sample of the composition to 105xc2x0 C. to 110xc2x0 C. for 1-2 hours to drive off the volatile material, and subsequently measuring relative weight loss. As aforementioned, although the compositions can be liquid coating compositions, they also can be formulated as powder coating compositions.
Where the basecoat is not formed from a composition of the present invention (but the topcoat is formed from a curable coating composition of the present invention) the coating composition of the basecoat in the color-plus-clear system can be any of the compositions useful in coatings applications, particularly automotive applications. The coating composition of the basecoat can comprise a resinous binder and a pigment to act as the colorant. Nonlimiting examples of resinous binders are acrylic polymers, polyesters, alkyds, and polyurethanes.
The resinous binders for the basecoat can be organic solvent-based materials such as those described in U.S. Pat. No. 4,220,679, note column 2, line 24 continuing through column 4, line 40, which portions are incorporated by reference. Also, water-based coating compositions such as those described in U.S. Pat. Nos. 4,403,003, 4,147,679 and 5,071,904 can be used as the binder in the basecoat composition. These U.S. patents are incorporated herein by reference.
The basecoat composition can comprise one or more pigments as colorants. Nonlimiting examples of suitable metallic pigments include aluminum flake, copper bronze flake, and metal oxide coated mica.
Besides the metallic pigments, the basecoat compositions can contain nonmetallic color pigments conventionally used in surface coatings such as, for example, inorganic pigments such as titanium dioxide, iron oxide, chromium oxide, lead chromate, and carbon black; and organic pigments such as phthalocyanine blue and phthalocyanine green.
Optional ingredients in the basecoat composition can comprise those which are well known in the art of formulating surface coatings and can comprise surface active agents, flow control agents, thixotropic agents, fillers, anti-gassing agents, organic co-solvents, catalysts, and other customary auxiliaries. Nonlimiting examples of these materials and suitable amounts are described in U.S. Pat. Nos. 4,220,679; 4,403,003; 4,147,769; and 5,071,904, which patents are incorporated herein by reference.
The basecoat compositions can be applied to the substrate by any conventional coating technique such as brushing, spraying, dipping, or flowing. Spray techniques and equipment for air spraying, airless spray, and electrostatic spraying in either manual or automatic methods, known in the art can be used.
During application of the basecoat to the substrate, the film thickness of the basecoat formed on the substrate can range from 0.1 to 5 mils. In another embodiment, the film thickness of the basecoat formed on the substrate can range 0.1 to 1 mils, and can be 0.4 mils.
After forming a film of the basecoat on the substrate, the basecoat can be cured or alternatively given a drying step in which solvent is driven out of the basecoat film by heating or an air drying period before application of the clearcoat. Suitable drying conditions may depend on the particular basecoat composition, and on the ambient humidity if the composition is water-borne, but a drying time from 1 to 15 minutes at a temperature of 75xc2x0 to 200xc2x0 F. (21xc2x0 to 93xc2x0 C.) can be adequate.
The transparent or clear topcoat composition can be applied to the basecoat by any conventional coating technique, including, but not limited to, compressed air spraying, electrostatic spraying, and either manual or automatic methods. The transparent topcoat can be applied to a cured or to a dried basecoat before the basecoat has been cured. In the latter instance, the two coatings can then be heated to cure both coating layers simultaneously. Typical curing conditions can range from 50xc2x0 F. to 475xc2x0 F. (10xc2x0 C. to 246xc2x0 C.) for 1 to 30 minutes. The clearcoating thickness (dry film thickness) can be 1 to 6 mils (25.4 to 152.4 micrometers).
A second topcoat coating composition can be applied to the first topcoat to form a xe2x80x9cclear-on-clearxe2x80x9d topcoat. The first topcoat coating composition can be applied over the basecoat as described above. The second topcoat coating composition can be applied to a cured or to a dried first topcoat before the basecoat and first topcoat have been cured. The basecoat, the first topcoat and the second topcoat can then be heated to cure the three coatings simultaneously.
It should be understood that the second transparent topcoat and the first transparent topcoat coating compositions can be the same or different provided that, when applied wet-on-wet, one topcoat does not substantially interfere with the curing of the other for example by inhibiting solvent/water evaporation from a lower layer. Moreover, the first topcoat, the second topcoat or both can be the curable coating composition of the present invention. Alternatively, only one of the first topcoat and the second topcoat is formed from the curable coating composition of the present invention.
In this instance, the topcoat that does not comprise the curable coating composition of the present invention can include any of the crosslinkable coating compositions comprising at least one thermosettable coating material and at least one curing agent. Suitable waterborne clearcoats for this purpose are disclosed in U.S. Pat. No. 5,098,947 (incorporated by reference herein) and are based on water-soluble acrylic resins. Useful solvent borne clearcoats are disclosed in U.S. Pat. Nos. 5,196,485 and 5,814,410 (incorporated by reference herein) and include polyepoxides and polyacid curing agents. Suitable powder clearcoats for this purpose are described in U.S. Pat. No. 5,663,240 (incorporated by reference herein) and include epoxy functional acrylic copolymers and polycarboxylic acid curing agents.
Typically, after forming the first topcoat over the basecoat, the first topcoat is given a drying step in which solvent is driven out of the film by heating or, alternatively, an air drying period or curing step before application of the second topcoat. Suitable drying conditions will depend on the particular first topcoat composition, and on the ambient humidity if the composition is water-borne, but, in general, a drying time from 1 to 15 minutes at a temperature of 75xc2x0 F. to 200xc2x0 F. (21xc2x0 C. to 93xc2x0 C.) will be adequate.
The film-forming composition of the present invention when employed as a second topcoat coating composition can be applied as described above for the first topcoat by any conventional coating application technique. Curing conditions can be those described above for the topcoat. The second topcoating dry film thickness can range from 0.1 to 3 mils (7.5 micrometers to 75 micrometers).
It should be mentioned that the coating compositions of the present invention can be advantageously formulated as a xe2x80x9cmonocoatxe2x80x9d, that is a coating which forms essentially one coating layer when applied to a substrate. The monocoat coating composition can be pigmented. Nonlimiting examples of suitable pigments include those mentioned above. When employed as a monocoat, the coating compositions of the present invention can be applied (by any of the conventional application techniques discussed above) in two or more successive coats, and, in certain instances can be applied with only an ambient flash period between coats. The multi-coats when cured can form essentially one coating layer.
In one embodiment, the present invention is directed to a method of repairing a multi-layer composite coating comprising a base coat formed on a substrate from a film-forming base coating composition and a first top coat deposited over at least a portion of the base coat, the first top coat formed from a first film-forming top coating composition comprising any of the foregoing coating compositions, the method comprising locating an area of the composite coating which is flawed, and applying a repair top coat film-forming composition to the flawed area after the flawed area has been prepared for repairing. The repair top coat film-forming composition can comprise a film-forming composition which is the same or different from the first top coat film-forming composition. The flawed area can be any coating blemish that cannot be polished out, for example dirt particles in the coating surface. The flawed area typically can be abraded or sanded to remove such coating blemishes. In a repair carried out in accordance with the method of the present invention, the first top coating can provide excellent intercoat adhesion with the subsequently applied repair top coating.
The coating compositions of the present invention can provide cured coatings having excellent intercoat or interlayer adhesion to subsequently applied coating layers. For example, any of the aforementioned substantially pigment-free coating compositions can be applied as a transparent clearcoat in a color-plus-clear coating system as discussed above. In the event of damage to the cured coating system causing a surface defect, it may be necessary to prepare the damaged area for repair with a subsequently applied clear coat composition. The coating compositions of the present invention can provide excellent intercoat adhesion between the first clear coat layer and the subsequently applied repair clear coat layer. Likewise, when used as a top coat composition, the coating compositions of the present invention also provide excellent interlayer adhesion between the cured top coat and a subsequently applied windshield adhesive without the intervening step of applying an adhesion promoting primer.